Engineering 
Library 


RAILWAY  SIGNALING 


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RAILWAY  SIGNALING 


BY 

EVERETT  EDGAR  KING 

MEMBER   OF   THE  AMERICAN  RAILWAY  ASSOCIATION,   SIGNAL  SECTION;  MEMBER   OF   THE 

AMERICAN'  RAILWAY  ENGINEERING  ASSOCIATION;  ASSOCIATE  MEMBER   OF 

THE  AMERICAN  SOCIETY  OF  CIVIL  ENGINEEBS;  PROFE88OB 

OF   RAILWAY  CIVIL  ENGINEERING   IN   THE 

UNIVERSITY  OF  ILLINOIS. 


FIRST  EDITION 


McGRAW-HILL  BOOK  COMPANY,  INC. 
NEW  YORK:  370  SEVENTH  AVENUE 

LONDON:  6  &  8  BOUVERIE  ST.,  E.  C.  4 
1921 


COPYRIGHT,  1921,  BY  THE 
McGRAw-HiLL  BOOK  COMPANY,  INC. 


THE     MAPI.B:     J'KKSS     YORK    PA 


PREFACE 

v 

It  is  the  purpose  of  this  boqk  to  collect  from  various  sources 
that  which  is  already  in  use  in  common  practice  in  the  fieldjef^ 
railway  signaling  and  to  present  it  in  text-book  form  suitable  for 
the  beginner  in  his  study  of  this  subject.  Much  of  the  descriptive 
material  and  many  of  the  drawings  were  furnished  by  the  various 
signal  and  supply  companies  specially  for  this  book.  Otrier 
descriptions  and  drawings  were  taken  from  catalogues  and 
descriptive  literature  issued  by  these  companies.  I  have  not 
included  any  thing  concerning  specifications  for  the  construction, 
installation  and  maintenance  of  materials.  This  is  a  voluminous 
subject  in  itself;  besides,  specifications  for  practically  every  item  of 
equipment  that  enters  into  railway  signaling  are  provided  for  in 
the  Manual  of  the  American  Railway  Association,  Signal  Section. 

In  a  few  cases,  I  have  quoted  from  the  Proceedings  of  the 
American  Railway  Engineering  Association,  from  the  Signal 
Dictionary  and  from  the  Railway  Signal  Engineer.  As  I  have 
drawn  so  largely  from  the  Proceedings  of  the  Railway  Signal 
Association,  it  might  be  pertinent  to  state  briefly  that  in  its 
early  days  the  organization  was  known  as  the  Railway  Signaling 
Club.  Later  it  changed  its  name  to  the  Railway  Signal  Associa- 
tion; and  recently  during  the  time  when  the  railways  were  under 
the  supervision  of  the  Director  General  of  Railroads,  United 
States  Railroad  Administration,  the  organization  amalgamated 
with  the  American  Railway  Association  and  took  the  name  which 
it  still  retains,  the  American  Railway  Association,  Signal  Section. 
I  might  state  in  this  connection,  also,  that  the  Manual  and  all  the 
Proceedings  of  the  organization  under  both  the  old  and  new  re- 
gimes may  be  obtained  from  the  Secretary,  Mr.  H.  S.  Balliet,  75 
Church  St.,  New  York. 

I  want  to  express  my  appreciation  for  the  help  received  from 
all  sources,  for  the  material  furnished,  for  the  suggestions  offered 
and  for  the  corrections  made  in  the  preparation  of  the  manu- 
script. I  am  especially  indebted  to  the  Union  Switch  and  Signal 
Company,  the  General  Railway  Signal  Company,  The  Federal 
Signal  Company,  and  the  Hall  Switch  and  Signal  Company  for 


460152 


vi  PREFACE 

the  photographs  and  drawings  that  I  have  selected  and  used  for 
general  illustrations.  I  am  equally  indebted  to  all  the  companies 
that  have  furnished  photographs  and  drawings  that  illustrate 
their  particular  line  of  equipment.  I  am  likewise  indebted  to 
the  Board  of  Directors  of  the  American  Railway  Association, 
Signal  Section,  for  permitting  me  to  use  the  many  cuts  and  quo- 
tations that  I  have  included  in  the  text.  I  appreciate  very  much 
the  assistance  given  by  Mr.  G.  A.  Blackmore  of  the  Union  Switch 
and  Signal  Company,  by  Mr.  A.  G.  Moore  of  the  General  Railway 
Signal  Company,  and  Mr.  S.  J.  Turreff  of  the  Federal  Signal 
Company.  I  am  especially  grateful  to  Mr.  Balliet  for  sugges- 
tions and  corrections  that  he  has  offered  in  the  preparation  of  the 
manuscript,  and  to  Mr.  S.  E.  Gillespie  for  his  kindness  in  prepar- 
ing some  of  the  material  for  the  original  manuscript  and  for 
his  valuable  suggestions  while  reviewing  and  proof-reading  the 
major  portion  of  the  remainder  of  it. 

E.  E.  KING. 
URBAN  A,  ILL. 
September,  1921. 


CONTENTS 

CHAPTER  I 

PRELIMINARY 
ART.  pAGE 

1.  Introductory 1 

2.  History 1 

3.  Organization 2 

4.  Rules  for  Signal  Supervisors  and  Signal  Foremen 5 

5.  Commissions 7 


CHAPTER  II 
SIGNAL  INDICATIONS 

6.  Two-  and  Three-position  Semaphore  Signal  Indications 8 

7.  Color  Lights  for  Day  Indications 11 

8.  Position-light  Signals 12 

9.  Disc  Signals 14 

10.  Take  Siding  Signal 17 

11.  Relative  Location  of  Signals  and  Tracks 19 

CHAPTER  III 
INTERLOCKING 

12.  Definition 22 

13.  Object 22 

14.  General  Plan 23 

15.  General  Order  of  Locking  Signals  and  Derails 25 

16.  Locking  Sheet 26 

17.  Diverging  Routes 28 

18.  Movable  Bridge  Interlocking 30 

19.  Requirements  for  the  Protection  of  Traffic  at  Movable  Bridges  .  32 

20.  Track  Diagram  and  Manipulation  Chart 35 

CHAPTER  IV 

MECHANICAL  INTERLOCKING 
INTERLOCKING  MACHINES 

21.  General 36 

22.  Horizontal  Locking 36 

23.  Special  Locking 39 

24.  Vertical  Locking 40 

vii 


viii  CONTENTS 

ART.  PAGE 

25.  Special  Locking ' 42 

26.  The  Dog  Chart 44 

27.  Stevens  Interlocking  Machine 48 

CHAPTER  V 
MECHANICAL  INTERLOCKING 

OTHER  EQUIPMENT 

28.  Leadouts 49 

29.  Pipes  and  Couplings 50 

30.  Stuffing  Box 50 

31.  Pipe  Carriers .'.....  50 

32.  Compensators 51 

33.  Field  Construction  of  Pipe  Lines 55 

34.  Horizontal  Cranks  and  Radial  Arms 57 

35.  Crank,  Wheel,  Compensator,  and  Pipe  Carrier  Foundations   ...  58 

36.  Facing  Point  Lock 59 

37.  Switch  and  Lock  Movement 59 

38.  Detector  Bar  . 60 

39.  Bolt  Lock 60 

40.  Head  Rod  and  Switch  Adjustment .62 

41.  Lock  Rod 63 

42.  Derails 65 

43.  Crossing  Bars 66 

44.  Semaphore  Signals 67 

45.  Dwarf  Signals 69 

46.  Time  Lock 69 

47.  Calling-on  Arm 73 

48.  Movable  Bridge  Couplers  and  Locks 74 

49.  Rules 75 

CHAPTER  VI 
ELECTRO- PNEUMATIC  INTERLOCKING 

50.  Ah-  Supply 78 

51.  Electricity 80 

52.  General  Sequence  in  Power  Interlocking 80 

53.  Interlocking  Machine 81 

54.  Mechanism  for  Throwing  Switches  and  Derails 87 

55.  Indication  Circuit  Controller 90 

56.  Indication  Relays  ...... 90 

57.  Detector  Locking.    ..-.>.. 94 

58.  "SS"  Control 94 

59.  Throwing  a  Switch 94 

60.  Signal  Operating  Mechanism 98 

61.  Operating  a  Signal. 99 

62.  Advantages ". 101 


CONTENTS  ix 
CHAPTER  VII 
ELECTRIC  INTERLOCKING 

GENERAL  RAILWAY  SIGNAL  COMPANY  SYSTEM 

IRT.  PAGE 

63.  Electricity 102 

64.  Operating  Switchboard  .    .....    ...    ....    .    .  •.    .    .    .    .    .  102 

65.  Interlocking  Machine.    .    .    .    . 103 

66.  Switch  Lever  Wiring ;.-......  107 

67.  Model  2  Switch  Machine  .    .  ' 108 

68.  Model  4  Switch  Machine 113 

69.  Model  5  Switch  Machine  .    .   .    ...    .    .    ....    .    .    ...    .  113 

70.  Semi-automatic  Signal  Control 115 

71.  Dwarf  Signals 118 

72.  Cross  Protection /-...-. 119 

73.  Alternating-current  Interlocking 121 

74.  Illuminated  Track  Diagram 122 

75.  Electro-mechanical  Interlocking  Machine 123 

UNION  SWITCH  AND  SIGNAL  COMPANY  TYPE  "F"  SYSTEM 

76.  General 124 

77.  Power  Supply 124 

78.  Interlocking  Machine. 124 

79.  Power  Mains 125 

80.  The  Indicating  System 127 

81.  Style  "  M  "  Switch  Movement 128 

82.  "SS"  Control 131 

83.  Auxiliary  Features 133 

84.  Union   "S-7"  and  "S-8"  Electro-mechanical  Interlocking  Ma- 

chines   133 

85.  Union  "P-5"  Electro-mechanical  Machine 135 

FEDERAL  SIGNAL  COMPANY  SYSTEM 

86.  Interlocking  Machine 135 

87.  Type  41  Switch  Machine  .   .   * 138 

88.  Switch  Machine  Control  and  Indication  Circuits .    .  141 

89.  Federal  Electro-mechanical  Interlocking  Machine 143 

HALL  SWITCH  AND  SIGNAL  COMPANY  SYSTEM 

90.  Interlocking  Machine . 144 

91.  Switch  Movement 145 

92.  Switch  Operating  Circuits .    .....    .    .    ...........  146 

93.  Signal  Operating  Circuits <    .....  146 

94.  Indication  Current 148 

95.  Switch  Indication  Circuit 148 

96.  Signal  Indication  Circuit 148 


X  CONTENTS 

CHAPTER  VIII 

DIRECT-CURRENT  TRACK  CIRCUITS 

ART.  PAGE 

97.  Track  Circuits 149 

98.  Cut  Sections 150 

99.  Fouling  Circuits 151 

100.  Insulated  Rail  Joints 151 

101.  Rail  Bonds  for  Track  Circuits 152 

102.  Neutral  Relay 152 

103.  Polarized  Relays 156 

104.  Track  and  Signal  Batteries 157 

105.  Battery  Wells  and  Battery  Chutes 160 

106.  Cable  and  Relay  Posts 160 

107.  Trunking 161 

108.  Insulated  Head,  Front,  and  Tie  Rods 162 

109.  Lightning  Arresters 162 

CHAPTER  IX 
ELECTRIC  LOCKING 

110.  Wiring  Diagrams  for  Electric  Locks 166 

111.  Section  Locking 171 

112.  Screw  Release 173 

113.  Clock-work  Time  Release 173 

114.  Approach  Locking 174 

115.  Route  Locking 176 

116.  Sectional  Route  Locking 177 

117.  Stick  Locking 177 

118.  Stick  Relay 179 

119.  Check  Locking ' 179 

120.  Union  Electro-mechanical  Slot 180 

121.  Hall  Electro-mechanical  Slot 183 

122.  Tower  Indicators ' 185 

CHAPTER  X 
MANUAL  BLOCK  SYSTEM 

THE  MANUAL  BLOCK 

123.  General  Description 186 

THE    CONTROLLED-MANUAL    BLOCK 

124.  General  Description 187 

THE  ELECTRIC  TRAIN  STAFF 

125.  General 189 

126.  Operation  of  the  Absolute  Staff  Instrument 190 

127.  The  Permissive  Staff 194 

128.  Intermediate  Siding  and  Junction  Instruments 196 

129.  Pusher  Attachment .197 


CONTENTS  xi 

CHAPTER  XI 
AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK 

GENERAL 

ART.  PAGE 

130.  Object 198 

131.  Location  of  Signals 199 

132.  Two-position  Semaphore  Signaling 201 

133.  Three-position   Signaling 202 

134.  Overlap  Systems 203 

135.  Absolute  and  Permissive  Signaling  on  Double  Track 203 

136.  Three-block  Indication  Scheme 206 

137.  Numbering  Automatic  Signal  Posts 206 

CHAPTER  XII 

AUTOMATIC   BLOCK   SIGNALING   ON   DOUBLE   TRACK 

DIRECT-CURRENT  TRACK  CIRCUITS 

NORMAL  CLEAR  SIGNALS 

138.  Two-position  Signal  Circuits 208 

139.  Two-position  Polarized  Track  Circuits 209 

140.  Three-position  Signal  Circuits 211 

141.  Three-position  Polarized  Track  Circuits .    ....... 213 

NORMAL  DANGER  SIGNALS 

142.  Two-position  Signal  Circuits 213 

SWITCH,  CURVE,  AND  SIDING  PROTECTION 

143.  Switch  Indicators 214 

144.  Switch  Box ,. 215 

145.  Signals  for  Outlying  Switches  and  Obscure  Curves 216 

CHAPTER  XIII 

AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK 
AS  ALTERNATING  CURRENT 

146.  Introductory 217 

SINGLE-RAIL  RETURN 

147.  Direct-current  Propulsion 218 

148.  Impedance  Coil 221 

149.  Track  Transformer 222 

DOUBLE-RAIL  RETURN 

150.  Direct-current  Propulsion 222 

151.  Alternating-current  Propulsion • 227 

ALTERNATING-CURRENT  SIGNALING  ON  STEAM  ROADS 

152.  General 227 


xii  CONTENTS 

TRANSFORMERS 

ART.  PAGE 

153.  General .    .    ^  ;   >    .    .    .    .    .    .    .    .  228 

ALTERNATING-CURRENT  RELAYS 

154.  General 230 

UNION  SWITCH  AND  SIGNAL  COMPANY  DESIGNS 

155.  Vane  Type ........ 230 

156.  Ironless  Galvanometer  Type.    .......  .,  .    . 231 

157.  Iron  Core  Galvanometer  Type ......    .    .    .  232 

158.  Centrifugal  Frequency  Relay .    ,.. 233 

159.  Radial  Contact  Polyphase  Induction  Type   .    .    ...    .    ...  .    .    .  234 

GENERAL  RAILWAY  SIGNAL  COMPANY  DESIGNS 

160.  Universal  Alternating  Current  Relay .  234 

161.  Models  2A  and  2B  Two-  and  Three-position  Relays 235 

162.  Model  2A  Two-position  Centrifugal  Frequency  Relay 236 

ALTERNATING-CURRENT  TRACK  AND  SIGNAL  CIRCUITS 

163.  Two-position  Signals 237 

164.  Three-position  Signals .    .  240 

CHAPTER  XIV 

AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK 

165.  General 249 

166.  Union  General  and  Special  Plans— TDB  System 249 

167.  General  Railway  Signal,  General,  and  Special  Plans,  —A.  P.  Block 

System 259 

168.  Other  Installations 262 

CHAPTER  XV 

SIGNAL  MECHANISMS 

TWO-POSITION  SIGNALS 

169.  Hall  Disc  Signal ] 271 

170.  Union  Style  "B"  Signal 272 

THREE-POSITION  SIGNALS 

171.  Union  Electro-pneumatic  Signal 275 

172.  Union  Style  "S"  Signal 275 

173.  Union  Style  "T-2"  Signal 276 

174.  General  Railway  Signal  Model  "2A"  Signal 279 

175.  Hall  Three-position  Style  "K"  Signal 283 

176.  Hall  Style  "L"  Signal , 284 

177.  Federal  Three-position  Type  •' 4"  Signal 285 


CONTENTS  xiii 

AUTOMATIC  STOPS 

ART.  PAGE 

178.  Motor-operated  Automatic  Stops 288 

LIGHT  SIGNALS 

179.  General 288 

COLOR-LIGHT  SIGNALS 

180.  Long-range  Type 291 

181.  Medium-range  Outdoor  Type 293 

182.  Short-range  Subway  and  Tunnel  Type 297 

POSITION-LIGHT  SIGNALS 

183.  Long-range 299 

184.  Short-range  or  Dwarf 301 

CHAPTER  XVI 
HIGHWAY  CROSSING  SIGNALS 

185.  General 302 

186.  Highway  Crossing  Signals 302 

187.  Highway  Crossing  Signal  Circuits 305 

188.  Interlocking  Relay .306 

189.  Hoeschen  Bell  System   ....  .308 

190.  AGA  Highway  Danger  Signals 315 

APPENDIX  A 

Rules  Governing  the  Construction,   Maintenance    and  Operation  of 

Interlocking  Plants .  318-324 

APPENDIX  B 
PART  I 

Signal  Aspects 325-327 

PART  II 
Symbols  Recommended  by  the  Railway  Signal  Association ....   328-340 

APPENDIX  C 

A  Definition  of  Terms  Used  in  Railway  Signaling 341-362 

Index.  363 


RAILWAY  SIGNALING 


CHAPTER  1 
PRELIMINARY 

1.  Introductory.— ^-Practically  the  only  purpose  a  railroad  has 
is  to  give  train  service  to  the  public  and  its  industries;  and 
whatever  will  facilitate  and  expedite  train  movements  to  the  best 
advantage  to  serve  this  purpose  with  a  reasonable  expenditure  of 
capital  will  work  to  the  best  interests  of  the  public  generally. 
As  the  number  of  trains  increases  and  their  speed,  weight,  and 
length  grow  greater  in  the  effort  to  handle  the  continually  increas- 
ing volume  of  traffic,  the  demands  for  safe  and  efficient  methods 
of  train  operation  become  more  urgent.     A  great  many  factors 
enter  into  the  success  of  railroad  transportation,  among  which 
are  the  motive  power  and  train  equipment,  the  track  and  road- 
way, the  signal  systems  and  methods  of  despatching  trains,  and 
the  personnel  of  the  employees  from  the  office  boy  to  the  manager. 
This  text  deals  only  with  signaling;  and  the  reader  should  bear 
in  mind  that  signaling  is  a  means  to  an  end  and  not  the  end 
itself. 

2.  History. — An  early  history  of  railway  signaling  in  America 
written  by  Mr.  J.  A.  Anderson  and  published  in  the  March  5,  1909 
issue  of  the  Railway  Age  Gazette  and  reprinted  in  the  1909  Volume 
of  the  Proceedings  of  the  Railway  Signal  Association^  gave  1870 
as  the  date  for  the  first  interlocking  plant  and  1863  as  the  date^ 
for  the  first  block  system.     The  interlocking  plalit  was  installed 
at  Trenton,  N.  J.,  on  the  line  of  the  United  New  Jersey  Canal 
and  Railroad  Companies,  afterwards  leased  by  the  Pennsylvania 
Railroad   Company.     The   machine   was   built   by  Saxby  and 
Farmer  of  London  after  the  same  pattern  as  those  they  had  built 
and  installed  on  lines  in  England.     It  was  built  principally  as 
an  experiment,  and  from  this  humble  beginning  the  interlocking 
plant  has  been  installed  wherever  important  railroad  crossings 
and  terminals  have  been  established. 

1 


2  RAILWAY  SIGNALING 


The  block  system  was  introduced  by  the  same  company  on  the 
line  between  New  Brunswick  and  Philadelphia.  A  form  of  block 
signaling  had  been  proposed  in  England  as  early  as  1842,  but  its 
adoption  in  that  country  generally  was  very  limited  for  a  number 
of  years  afterwards.  The  system  established  in  America  gave 
positive  indications  by  means  of  signals,  and  went  a  long  way  in 
eliminating  many  of  the  difficulties  involved  in  the  older  foreign 
systems. 

In  the  early  days  practically  all  of  the  signal  appliances  were 
of  a  mechanical  type,  more  or  less  simple  in  construction,  and 
did  not  require  men  especially  trained  for  their  maintenance 
and  operation.  Improvements  were  made  from  time  to  time  to 
keep  pace  with  the  demands  of  transportation.  The  public 
saw  in  signaling  possibilities  for  greater  safety;  the  railroads  saw 
opportunities  for  both  safety  and  efficiency  in  operation.  Later, 
electricity  was  applied  to  solve  the  signal  problems,  and  it  became 
a  potent  factor  in  the  growth  of  the  signal  industry.  More  and 
more  was  it  utilized  to  replace  the  human  element  in  signal 
operation.  As  the  systems  grew,  organizations  grew  with  them. 
As  the  equipment  became  more  complicated,  there  came  the 
demand  for  specialists,  men  who  were  better  trained,  and  who 
could  give  all  their  time  and  attention  to  this  particular  kind  of 
work.  Power  interlocking  was  introduced  and  the  track  circuit 
became  well  established.  Gradually  a  reliable  system  has  thus 
been  developed  to  meet  the  needs  of  the  situation.  Interlocking 
appliances  have  been  made  better  and  automatic  block  systems 
perfected  until  accidents  rarely  occur  on  account  of  signal 
failures.  The  service  has  been  so  improved  that  many  roads 
have  been  able  largely  to  eliminate  the  train  order  as  a  factor  in 
despatching  trains. 

3.  Organization. — The  field  of  signal  engineering  is  a  distinct 
one  and  embraces  construction,  installation,  operation  and 
maintenance  of  railway  signals.  The  equipment  is  practically 
all  made  by  signal  manufacturers  and  is  bought  by  the  railroads 
at  a  unit  price  or  on  a  contract  basis.  The  companies  that  make 
the  equipment  may  also  install  it,  or  the  railroad  may  take  the 
equipment  when  it  is  delivered  and  install  it  with  its  own  con- 
struction forces.  In  nearly  all  cases  the  maintenance  is  handled 
by  railroad  forces. 

The  general  type  of  organization  that  prevails  on  a  road  will 
determine,  in  a  measure  at  least,  the  particular  organization  of 


PRELIMINARY  3 

the  signal  department.  In  the  departmental  system,  the  signal 
engineer  reports  to  the  chief  engineer  and  has  charge  of  all  the 
work  of  the  signal  department.  He  makes  requisitions  for  new 
equipment,  has  charge  of  all  materials  and  supplies  on  hand  and 
directs  the  work  of  the  organization.  In  the  divisional  system, 
the  signal  engineer  reports  to  the  chief  engineer  as  before  and  has 
immediate  charge  of  standards  and  construction.  The  divisional 
maintenance  is  in  charge  of  the  signal  supervisor  who  reports 
directly  to  the  division  superintendent  or  division  engineer.  In 
this  connection  he  is  assisted  in  an  advisory  way  by  the  signal 
engineer.  The  following  article  written  by  Mr.  A.  G.  Shaver 
and  published  in  the  September,  1917,  issue  of  the  Signal  Engineer 
states  some  of  the  requirements  for  success  as  a  signal  engineer 
and  outlines  a  typical  signal  department  organization:1 

.  "Four  qualifications  are  indispensable  in  every  man  that  he  may  be 
a  good  signal  engineer;  he  must  have  had  experience  in  railway  signal- 
ing; he  must  have  a  technical  education;  he  must  be  a  good  executive, 
and  he  must  have  a  general  knowledge  of  railroading.  Any  signal 
engineer  who  does  not  have  an  intimate  knowledge  of  signaling,  such  as 
one  gets  from  actual  service  as  laborer,  skilled  workman,  foreman  or 
maintainer,  is  not  only  greatly  handicapped,  but  is  more  or  less  inefficient 
to  his  company.  The  technical  education  need  not  be  that  acquired  by 
a  course  in  college,  though  that  is  an  advantage;  it  must  include  a 
very  complete  knowledge  of  the  general  principles  of  electricity,  an 
understanding  of  mechanics  and  a  familiarity  with  those  features  of 
civil  engineering  concerned  in  railroad  construction.  Since  the  job  of 
signal  engineer  on  most  railroads  carries  with  it  a  command  over  men, 
executive  ability  is  necessary  for  effective  results.  In  railroading  a 
knowledge  of  construction,  maintenance  and  operation  is  needed.  The 
construction  of  the  railroad  and  the  signaling  must  harmonize  and  be 
maintained  and  operated  together;  it  is  particularly  necessary  to  know 
how  trains  are  run  and  what  the  facilities  must  be  for  trains  to  be 
operated  to  the  best  advantage. 

"Signal  departments  vary  considerably  in  make-up  and  jurisdiction, 
having  often  been  gradually  built  up  from  some  old  arbitrarily  established 
basis  and  having  to  meet  conditions  peculiar  to  the  railroad  itself. 
There  are,  doubtless,  few  signal  department  organizations  entirely 
satisfactory  to  the  signal  engineer  in  charge. 

"An  example  of  a  suitable  signal  department  organization  for  a  large 
road  is  shown  by  the  diagram  Fig.  1.  The  assistant  signal  engineer, 
the  general  inspector,  the  superintendent  of  signal  construction,  the  chief 

1  Page  276. 


4  RAILWAY  SIGNALING 

draftsman  and  the  chief  clerk  all  report  to  the  signal  engineer.  The 
assistant  signal  engineer  is  in  authority  next  to  the  signal  engineer  and 
has  charge  of  all  matters  pertaining  to  maintenance  and  operation  and 
the  preparation  of  standards  and  specifications.  The  general  signal 
inspector  has  supervision  over  all  inspections,  investigations,  tests, 
experiments,  educational  matters  and  the  signal  shop.  The  superin- 
tendent of  signal  construction  has  charge  of  all  work  of  construction, 
reconstruction  and  changes.  The  chief  draftsman  has  the  preparation 
of  estimates  and  drawings,  the  designing  of  circuits  and  apparatus  and, 
under  the  assistant  signal  engineer,  the  making  of  standards  and  speci- 
fications. The  chief  clerk  has  authority  over  the  force  and  business 
of  the  office,  including  accounts,  statistics,  reports,  payrolls,  etc.  The 


|     Signal  Engineer      | 


Clerk      | 
| 

Asst.  Signal 
Engineer 

Isupt.  Signal 
Construction 

Force      | 

General 
Inspector 

Chief        |  1    Construction 
1           Draftsman    |  |        Foremen 

|    Superintendent      | 


|    Signal  Shop     | 


Educational 
Work 


Signal 
Supervisor' 


Drafting 
Force 


Construction 
Forces 


Maintenance 
Forces 


FIG.  1. — A  typical  signal  department  organization.      (Railway  Signal  Engineer.) 


signal  supervisor  reports  to  the  superintendent  in  all  matters  pertaining 
to  the  maintenance  and  operation  of  signals  and  to  the  assistant  signal 
engineer  on  technical  matters,  special  reports,  special  requisitions  and 
those  things  not  covered  by  standards  and  approved  practices;  he  is 
appointed  by  the  superintendent  on  approval  of  the  signal  engineer. 
The  signal  engineer  gives  to  the  superintendent  general  and  special  in- 
structions concerning  maintenance  and  operation  of  signals,  confers 
with  him  regarding  new  construction  proposed  and  authorized  and  as- 
sists to  get  efficient  results  from  the  signaling  in  service. 

"On  a  small  railroad  this  organization  may  be  varied  to  suit  condi- 
tions. Ordinarily  the  signal  engineer  would  have  direct  authority  over 
the  maintenance  and  operation  of  signals  as  well  as  construction  and 
other  matters,  and  his  organization  might  be  curtailed  as  to  the  number 
and  assignment  of  subordinates.  Indeed,  a  railroad  may  be  so  small, 
as  to  the  amount  of  signaling  it  has,  as  not  to  need  a  signal  department 


PRELIMINARY  5 

at  all.  The  care  of  its  signal  work  could  be  given  over  to  some  existing 
department  having  work  of  a  like  nature  and  expert  service  hired  as 
required." 

4.  Rules  for  Signal  Supervisors  and  Signal  Foremen. — In 

order  to  establish  a  high  grade  of  uniform  practice  among  signal 
supervisors  and  their  foremen,  the  following  rules  were  prepared 
and  written  in  the  Manual  of  the  American  Railway  Engineering 
Association:1 

RULES  GOVERNING  SIGNAL  SUPERVISORS 

1.  Signal  Supervisors  shall  report  to  and  receive  instructions  from  the 
(Title) 

2.  They  shall  be  responsible  for  the  safe  condition  and  proper  maintenance 
of  signals  and  interlocking  plants.     They  must  make  temporary   repairs 
of  such  defects  as  may  endanger  or  delay  the  movement   of  trains,  and 
promptly  report  defective  conditions  to  the !T!*!.?1 

3.  They  must  make  frequent  inspections  of  signals  and  interlocking  plants 
and  have  necessary  repairs  made  as  promptly  as  conditions  require.    They 
must  see  that  all  failures  of  signals  and  interlocking  plants  are  promptly 
investigated  and  report  made  on  Form  No 

4.  They  shall,  as  necessary,  employ  men  for  carrying  out  the  duties  for 
which  they  are  responsible. 

5.  They  must  know  that  foremen  are  familiar  with  the  operating  rules 
in  regard  to  tram  signals  and  flagging,  arid  that  they  fully  understand  and 
comply  with  them. 

6.  They  must,  in  case  of  damage  to  signals  or  interlocking,  pronnotly  as- 
semble forces,  tools  and  materials,  and  make  necessary  repairs. 

7.  They  shall  investigate  and  report  on  accidents  which  may  be  attri- 
butable to  defects  in,  or  result  in  damage  to,  the  signal  apparatus. 

8.  They  shall  conform  to  the  prescribed  standards  and  plans  in  the  execu- 
tion of  work  under  their  charge. 

9.  They  must  know  that  foremen  are  supplied  with  tools  and  materials 
necessary  for  the  efficient  performance  of  their  duties,  and  see  that  these 
are  properly  used  and  cared  for. 

10.  They  must  not,  except  by  proper  authority,  permit  experimental 
trials  of  appliances  or  devices,  nor  give  out  information  of  the  results  of 
any  trial. 

11.  They  shall  keep  themselves  informed  in  regard  to  all  work  performed 
in  their  districts  by  contractors,  or  others  who  do  not  come  under  their 
charge,  see  that  nothing  is  done  by  them  that  will  interfere  with  the  safe 
operation  of  signals,  and  report  promptly  to  the  (.T^?.) 

if  the  work  is  not  done  in  accordance  with  the  prescribed  standards. 

12.  They  shall  have  immediate  supervision  of  work-train  service  for  the 
maintenance  of  signals  and  interlocking  plants  in  their  districts,  and  em- 
ploy such  service  only  when  authorized  by  the   (Title) 

1  Page  430,  1915  edition. 


6  RAILWAY  SIGNALING 

fS.  They  must  know  that  foremen  are  provided  with  the  rules,  circulars, 
forms,  special  instructions  and  safety  regulations  pertaining  to  their  duties, 
and  that  they  fully  understand  and  comply  with  them. 

RULES  GOVERNING  SIGNAL  FOREMEN 

1.  Signal  Foremen  shall  report  to  and  receive  instructions  from  the 

(Title) 

2.  They  shall  be  responsible  for  the  proper  inspection  and  safe  condition 
of  signals  and  interlocking  plants  under  their  charge,  and  shall  do  no  work 
thereon  that  will  interfere  with  the  safe  passage  of  trains,  except  under  proper 
protection. 

3.  They  must  make  such  inspection  of  the  signals  and  interlocking  plants 

in  their  districts  as  the £3**5i may  direct,  and  report 

all  defects  found  on  Form  No.  _ 

4.  They  shall  employ  men  as  the  (.Title) directs. 

They  must  treat  employees  with  consideration,  and  see  that  they  properly 
perform  their  duties.     They  must  discharge  men  who  are  incompetent  or 
neglect  their  duties,  but  in  no  case  shall  they  discharge  men  without  cause. 
They  must  keep  the  required  records  of  the  time  of  their  men  and  of  the 
materials  used. 

5.  They  must  each  have  a  copy  of  the  current  timetable,  and  be  thor- 
oughly familiar  with  the  rules  and  regulations  therein,  and  with  the  time 
of  trains  over  their  districts.     They  must  carefully  observe  signals  dis- 
played by  all  trains,  and  assure  themselves,  before  obstruct  ng  track,  that 
all  trains  and  sections  due  have  passed.     No  notice  will  be  given  of  extra 
trains,  and  employees  must  protect  themselves  as  prescribed  by  the  rules. 
Foremen  must  provide  themselves  with  reliable  watches,  and,  when  pos- 
sible, verify  time  daily  with  a  standard  clock  or  with  the  watches  of  other 
employees  who  are  required  to  have  the  standard  time. 

6.  They  must,  in  case  of  damage  to  signal  or  interlocking  apparatus  in 
their  districts,  promptly  proceed  to  the  place  with  the  men,  tools  and  mate- 
rials at  their  command  and  do  all  in  their  power  to  make  necessary  repairs. 

7.  They  shall  investigate  and  report  on  accidents  which  may  be  attri- 
butable to  defects  in,  or  result  in  damage  to,  the  signal  apparatus. 

8.  They  shall  conform  to  the  prescribed  standards,  plans  and  specifica- 
tions in  the  execution  of  the  work  under  their  charge. 

9.  They  shall  be  responsible  for  the  proper  care  and  use  of  tools  and  mate- 
rials necessary  for  the  efficient  performance  of  their  duties,  and  shall  make 
requisition  to  the  .(.T.1^.!?.)  from  time  to  time  as  additional 
supply  becomes  necessary. 

10.  They  must  not,  except  by  proper  authority,  permit    experimental 
trials  of  appliances  or  devices,  nor  give  out  information  of  the  results  of 
any  trial. 

11.  They  must  not  make  nor  permit  any  permanent  rearrangement  or 
change  in  the  signals  or  interlocking  plants  without  proper  authority. 

12.  They  must  thoroughly  understand  the  rules,  circulars,  forms,  special 
instructions  and  safety  regulations  pertaining  to  their  duties,  and  see  that 
they  are  complied  with. 


PRELIMINARY  7 

5.  Commissions. — The  Interstate  Commerce  Commission  and 
State  Railroad  or  Public  Utilities  Commissions  are  vitally  inter- 
ested in  railway  signaling,  but  their  interest  lies  wholly  on  the  side 
of  safety.  In  its  early  days  the  Interstate  Commerce  Commis- 
sion gave  attention  to  investigations  concerning  safety  in  signal 
systems,  and  in  1907  it  established  a  Block  Signal  and  Train 
Control  Board.  This  Board  was  charged  with  a  number  of 
duties,  among  which  were  those  of  making  investigations  in 
regard  to  block  signals,  automatic  stops  and  cab  signals,  and  other 
devices  that  were  produced  with  the  idea  of  promoting  safety  in 
railroad  operation.  As  block  signals  had  been  in  service  for  a 
sufficient  period  to  be  made  successful  in  operation,  the  Board 
gave  a  large  share  of  its  attention  to  automatic  stops  and  cab 
signals.  For  a  number  of  years  automatic  stops  have  been  used 
on  subway,  elevated  and  other  electric  lines,  but  their  application 
has  not  yet  been  extended  generally  to  steam  roads.  The  Block 
Signal  and  Train  Control  Board  passed  out  of  existence  in  1912, 
and  their  work  was  then  handled  by  the  Division  of  Safety  of  the 
Interstate  Commerce  Commission.  In  1917  the  name  of  the 
organization  was  changed  to  Bureau  of  Safety  of  the  Interstate 
Commerce  Commission. 

Many  of  the  state  commissions  have  formulated  rules  govern- 
ing the  installation  and  operation  of  interlocking  plants,  block 
signal  systems  and  other  appliances,  and  have  a  corps  of  inspec- 
tors to  see  that  their  requirements  are  fulfilled.  One  of  the  im- 
portant problems  that  the  state  commissions  have  to  face  is  the 
question  of  adequate  protection  for  vehicles  where  the  highways 
cross  the  railways  at  grade.  This  has  become  especially  serious 
in  recent  years  on  account  of  the  heavy  increase  in  automobile 
traffic  over  transcontinental  and  other  high-speed  routes. 


CHAPTER  II 
SIGNAL  INDICATIONS 

Signals  are  used  to  convey  certain  information  to  trainmen 
and  others  interested  in  railway  operation  that  they  may  be  able 
to  act  intelligently  with  safety  and  promptness  concerning  train 
movements.  Practically  all  of  the  information  given  by  signals 
is  intended  for  enginemen,  and  is  generally  conveyed  by  visual 
indications.  "Railway  Signaling"  is,  then,  that  branch  of  rail- 
way service  that  is  engaged  in  installing  and  operating  such 
equipment  and  appliances  adjacent  to  the  track  as  will  indicate  to 
an  engineman  whether  he  should  advance  his  train  or  stop  it. 

6.  Two-  and  Three-position  Semaphore  Signal  Indications. — 
The  day  indications  are  given  by  different  positions  of  semaphore 
arms,  by  colored  and  uncolored  lights,  or  by  discs;  while  night 
indications  are  given  entirely  by  colored  and  uncolored  lights. 
Signal  indications  may  be  either  two-position  or  three-position. 
Two-position  signals  require  a  home  and  distant  signal.  The 
home  signal  gives  final  authority  to  the  enginemen  while  the  dis- 
tant signal  merely  repeats  the  indications  of  the  home  signal; 
and  its  function  is  purely  cautionary. 

In  two-position  semaphore  signaling  the  home  blade  is  made 
with  a  square  end  for  interlocking  and  with  either  a  square  end 
or  a  pointed  end  for  block  signaling.  The  front  of  it  is  usually 
painted  red  with  a  white  stripe  near  its  outer  end  and  the  back  of 
it  white  with  a  black  stripe  near  the  end.  The  distant  blade  is 
made  with  a  V-shape  or  fish-tail  end.  The  front  of  it  is  generally 
painted  yellow  with  a  black  stripe  parallel  to  the  end  of  the  blade, 
or  green  with  a  white  or  red  stripe.  The  back  of  the  blade  is 
painted  white  with  a  black  stripe.]  A  few  roads  that  do  not  use 
this  notation,  paint  the  front  of  all  blades  yellow  with  a  black 
stripe,  and  the  back  black  with  or  without  a  white  stripe. 

[Three-position  blades  are  made  with  square  ends  for  inter- 
locking purposes  and  with  either  square  or  pointed  ends  for  block 
signaling.  Where  both  square  and  pointed  blades  are  used,  the 
square  end  blades  indicate  stop  and  stay  when  the  signal  indicates 
stop;  while  the  pointed  end  blades  indicate  stop  and  proceed  at 

8 


SIGNAL  INDICATIONS  9 

low  speed  when  the  signal  indicates  stop.  Stop  and  stay  is  al- 
ways the  stop  indication  at  interlocking  plants. 

The  front  side  of  three-position  blades  is  painted  red  with 
a  white  stripe  parallel  to  the  end  or  yellow  with  a  black  stripe. 
The  back  side  is  painted  white  with  a  black  stripe,  or  black  with 
or  without  a  white  stripe. 

Signal  blade  indications  are  given  in  either  the  lower  or  upper 
quadrant.  Two-position  signals  built  as  such  generally  operate 
the  blade  from  the  horizontal  into  the  lower  quadrant.  In  the  case 
of  the  home  signal,  the  horizontal  position  means  stop;  the 
inclined  position,  which  varies  from  45  to  75  degrees  below  the 
horizontal,  with  an  average  of  60  degrees,  means  proceed.  In  the 
case  of  the  distant  signal,  the  horizontal  position  means  caution 


FIG.  2. — Two-position  home  signal. 

and  indicates  that  the  home  signal  is  in  the  stop  position;  the  in- 
clined position  means  proceed  and  indicates  that  the  home  signal 
is  in  the  proceed  position.  An  engineman  may  pass  a  distant 
signal  set  at  caution,  but  he  must  be  prepared  to  stop  at  the  home 
signal  set  at  stop.  In  the  case  of  interlocking,  he  must  stop  and 
stay,  while  in  some  cases  in  block  signaling  he  may  proceed  after 
the  stop.  Figures  2  and  3  show  the  ordinary  two-position  home 
and  distant  semaphore  signals. 

Three-position  signals  may  operate  the  blade  in  either  the 
lower  or  upper  quadrant.  The  horizontal  position  means  stop; 
inclined  up  or  down  45  degrees  from  the  horizontal  means  cau- 
tion, the  first  signal  ahead  is  at  the  stop  indication;  up  or  down 
90  degrees  from  the  horizontal  means  proceed.  Figure  4  shows 
three-position  lower  and  upper  quadrant  semaphore  signals. 

The  upper  quadrant  signal  is  the  latest  development  of  blade 


10  RAILWAY  SIGNALING 

indications  and  possesses  some  advantages  over  lower  quadrant 
movements,  chief  among  which  is  the  fact  that  the  arm  does 


Yellow 


FIG.  3. — Two-position  distant  signal. 

not  require  a  counterweight  to  place  it  in  the  stop  position. 
This  is  of  considerable  importance  in  case  of  failure  of  signal 


Pact 


Yd  low 


Yellow 


Omen 


FIG.  4. — Three-position  lower  and  upper  quadrant  signals. 


operating  mechanisms.     Should  sleet  collect  on  the  blade  it  would 
tend  to  pull  the  upper  quadrant  signal  to  the  stop  position  and 


SIGNAL  INDICATIONS  11 

to  hold  the  lower  quadrant  signal  in  the  proceed  position.  There 
is  little  doubt,  too,  but  that  the  blade  giving  the  proceed  indi- 
cation in  the  upper  quadrant  can  be  seen  farther  by  enginemen 
than  one  giving  the  same  indication  in  the  lower  quadrant. 

Signal  light  indications  in  the  case  of  two-position  signals  are 
given  by  two  colors  in  the  home  and  two  in  the  distant  signal. 
A  red  light  in  the  home  signal  means  stop,  a  green  light  means 
proceed,  as  indicated  by  Fig.  2.  A  yellow  light  in  the  distant 
signal  means  caution,  a  green  light  means  proceed,  as  shown  by 
Fig.  3.  Some  roads  use  the  combination  red  and  white,  and 
green  and  white,  for  the  indications.  The  objections  raised 
against  the  white  light  are  that  it  might  be  confused  with  some 
other  light  or  might  be  the  result  of  a  broken  roundel.  In  the 
case  of  three-position  signals  a  red  light  means  stop,  a  yellow 
light  caution,  a  green  light  clear,  as  indicated  in  Fig.  4.  Some 
roads  use  the  combination  red,  green,  and  white,  but  the  same 
objections  hold  against  the  white  light.  Where  three-position 
signals  are  used  at  interlocking  plants,  not  in  block  signal  territory, 
the  home  and  distant  signals  are  wired  to  indicate  only  in  the  0 
and  90-degree  positions,  upper  and  lower  quadrants.  When 
used  where  automatic  block  signals  are  in  operation,  the  home  and 
distant  signals  indicate  also  in  the  45-degree  position,  a  caution 
indication  for  block  signaling,  but  proceed  for  interlocking. 

The  casting  in  the  two-position  signal  is  generally  made  with 
three  spectacles  in  which  the  upper  two  glasses,  called  roundels, 
are  the  same  color.  The  object  of  having  the  two  glasses  with  the 
same  color  is  to  give  a  continuous  stop  or  caution  indication 
until  the  signal  reaches  the  proceed  position.  The  three-position 
lower  quadrant  signal  frequently  has  four  spectacles,  the  extra 
one  being  made  to  provide  for  two  possible  positions  of  the  signal 
lamp.  Usually  the  lamp  is  on  the  side  of  the  post,  but  occasion- 
ally it  stands  on  top. 

7.  Color  Lights  for  Day  Indications. — Within  recent  years  it 
has  become  the  practice  on  manj^  electric  lines  and  even  on  some 
steam  roads  to  use  lights  for  giving  both  day  and  night  indica- 
tions. Where  large  and  powerful  lenses  are  used  in  connection 
with  reflectors  and  deep  hoods,  as  shown  in  Fig.  5,  the  lights  can 
be  seen  for  a  considerable  distance,  even  in  bright  sunlight.  For 
three-position  signaling  with  colored  lights  each  signal  will  have 
three  lenses,  red,  yellow,  and  green,  placed  vertically  with  the 
usual  arrangement  of  having  the  red  at  the  bottom,  the  yellow  / 


12 


RAILWAY  SIGNALING 


in  the  middle,  and  the  green  at  the  top.  The  range  of  vision 
varies  from  a  few  hundred  feet  for  subway  and  tunnel  signaling  to 
3,000  ft.  for  outdoor  signaling  where  the  light  must  be  distinctly 
seen  in  bright  sunlight  by  high-speed  trains.  There  must  be 
enough  spread  to  the  light  so  that  a  train  crew  can  readily  see  it 
as  they  approach  it  on  a  curve. 


FIG.  5. — Color-light  signal. 

8.  Position-light  Signals. — The  position-light  signals  first  came 
into  use  in  1915  at  the  time  the  Pennsylvania  Railroad  elec- 
trified its  line  between  Philadelphia  and  Paoli.  The  signal  is  a 
modification  of  the  semaphore  to  the  extent  that  the  indications 
are  given  by  electric  lamps  placed  in  rows  to  represent  the  positions 
of  the  blade  in  upper  quadrant  signaling.  Both  two-  and  three- 
position  signals  are  used  for  high-speed  lines  with  four  lights  in 
each  row  spaced  18  in.  apart  to  represent  the  different  positions 
of  the  signal  blade.  Yellow-tinted  lenses  are  used  with  the 
advantage  of  having  a  longer  range  of  vision.  The  lamps  for 
high  signals  are  provided  with  deep  hoods  and  with  metal  back- 
grounds. The  dwarfs  are  provided  with  two  lunar-white  lamps 
in  each  row  constructed  for  a  comparatively  short  range  of  vision. 

Light  signals  require  a  greater  current  than  semaphore  signals 


SIGNAL  INDICATIONS 


13 


for  continuous  normal  clear  indications,  for  it  requires  a  compara- 
tively small  amount  of  energy  to  hold  semaphores  to  the  proceed 
indication;  but  if  lights  could  be  wired  to  give  their  indications 
only  on  the  approach  of  trains,  they  would  use  a  very  small 
amount  of  current  and  extend  the  life  of  the  lamp  in  proportion. 
There  is  more  justification  for  using  lights  to  give  day  indications 
on  roads  that  use  alternating  current  for  signaling  or  propulsion 
than  on  those  that  use  the  battery  for  signaling.  As  the  current 
is  already  available  in  those  cases,  practically  no  additional  expense 
is  necessary  for  wiring. 


FIG.  6. — Position-light  signal. 


As  there  are  no  complicated  mechanisms  nor  moving  parts  as 
there  are  in  the  case  of  the  semaphore  signal,  the  chances  for 
failure  are  materially  reduced.  By  having  standard  light  indica- 
tions for  both  day  and  night  signaling  instead  of  two  distinct 
types,  the  semaphore  for  position  by  day  and  the  light  for  color  by 
night,  the  system  becomes  much  simplified.  The  lights  have 
another  advantage  that  there  are  no  exposed  parts,  such  as  the 
disc  or  blade  to  collect  sleet  and  ice,  thereby  tending  to  obscure 
the  indicatiofifT^Nyhe  following  conclusions  concerning  the  use  of 
light  signals  are  given  in  the  1917  volume  of  the  Proceedings  of 
the  Railway  Signal  Association:1 

1  Page  10. 


14  RAILWAY  SIGNALING 

I  First. — Colored  and  position-light  signals,  for  day  and  night  use,  by 
elimination  of  all  moving  parts  except  the  control  relays,  reduce  the 
number  of  failures. 

Second. — Light  signal  aspects  have  greater  visibility  and  range  under 
adverse  weather  and  background  conditions  than  the  semaphore,  while 
the  close  indications  compare  favorably. 

Third. — Light  signals  give  uniform  indications  at  all  times.  Other 
types  of  signals  give  the  indication  by  position  in  daylight,  by  color  at 
night,  and  by  both  during  transition  periods.  The  various  aspects  of 
the  position-light  signal  are  equal  in  intensity,  range  and  visibility. 

Fourth. — In  general  practice,  the  number  of  aspects  of  any  one  arm  of 
a  semaphore  is  limited  to  three.  With  the  position-light  signal,  four 
distinctive  positions  may  be  used,  while  the  number  of  indications 
given  by  colored-light  signals  is  limited  only  by  the  colors  available. 

Fifth. — Where  power  is  available,  the  cost  of  operating  light  signals 
is  less  than  for  operating  motor  signals. 

Sixth. — Current  consumption  under  normal  automatic  signal  condi- 
tions: 

Position-light  signals :  Four  5-watt  lamps — 20  watts. 

One  colored  light:  35  to  50  watts. 

For  interlockirtg  signals,  consumption  is  increased  depending  upon 
the  number  of  lights  displayed,  but  the  ratio  holds. 

Seventh. — Cost  of  maintenance  of  light  signals  is  considerably  less 
than  that  of  motor  signals,  and,  as  the  colored-light  signal  has  fewer 
lights  to  renew,  it  has  an  advantage  in  this  respect  over  the  position- 
light  signal. 

Eighth. — The  field  for  the  economical  use  of  light  signals  is  limited, 
as  noted  above,  to  points  where  power  is  available.  In  this  field,  the 
light  signals  have  advantages  over  other  types.  The  position-light 
signal  can  be  installed  at  any  location  where  clearance  will  permit  the 
present  standard  semaphore  to  be  erected.  The  colored-light  signal  can 
be  used  in  more  restricted  clearances. 

9.  Disc  Signals. — A  few  roads  are  using  the  disc  signal  for 
automatic  block  signaling  purposes.  It  operates  as  a  two- 
position  signal,  although  in  an  entirely  different  manner  from  the 
semaphore  type.  The  day  indications  are  given  by  colored  discs, 
a  red  disc  for  the  home  signal  and  a  yellow  or  green  one  for  the 
distant  signal.  Each  disc  operates  in  an  enclosed  case  mounted 
on  top  of  a  post  that  stands  in  the  same  relative  position  to  the 
track  as  does  the  semaphore  signal,  as  shown  in  Fig.  7.  To  give 
the  stop  or  caution  indication,  the  disc  swings  into  full  view 
entirely  covering  the  opening  in  the  front  of  the  banjo-shaped 
case,  as  shown  by  (a)  and  (6)  of  Fig.  8.  To  give  the  proceed 


SIGNAL  INDICATIONS 


15 


JPIG>  7 — Disc  signals  arranged  for  left-hand  running. 


(00 


FIG.  8. — Disc  signals. 


(a).    Home  Signal, 

Stop  Indication, 
Red  Disc, 
Red  Light. 

(c).     Home  Signal, 

Proceed  Indication, 
No  Disc, 
White  Light. 


(6).    Distant  Signal, 

Caution  Indication, 
Yellow  or  Green  Disc, 
Green  Light 


(d). 


Distant  Signal, 
Proceed  Indication, 
No  Disc, 
White  Light. 


16  RAILWAY  SIGNALING 

A.C.L.cmd  B.ft  O.R.R.  N.C.  &  S.T.L.R.R. 


Reflected 
WhiteUght 


(^•"Screen 


Normal  Take  Siding 


By  Day-White 

...ibght        ^  Better  "S" 
Ql or  Letter 

Illuminated 

Normal  Take  Siding 


M.  C    R.  R. 


No  Light  Disc  painted  Black 
N  orrna  I 


Freight  Take  Siding 
Q.  a  C    R. R. 


Reef 


Green 
Light- 


Stop 


Caution  Clear 

C.C.C    a   S  T    L    RY 


Take  Siding 


C 

C 

C 

m 

c 

By  Dcy-  White 

x—  >. 

s~~\ 

/^\ 

/fa\  By  Night-White 

^Ov 

vO// 

^O  } 

\^/  Letter  "Stf 

Nor 

mal                      Nor 

No  Light  or  Letter  -^ 
mal                      Nor 

mal                 Take  S 

Illumina  ted 
id  ing 

A.T.  ftS.F.RY.                                      MO.PAC 

ZH 

1      Green 
Light^- 

\y\       Yellow^ 
\\,    Light® 

^    Yellow  r 
Light  w- 

12 

Yellow 

-7      Green 

.         Yellow 

-•^'   ^ 

/>      Lights 

\      Light  r 

<\      Lightc^ 

^ 

..  ,  

HI 

—   .             _  .  ~~: 

m 

-White  Light 

—..              ~     .r^ 

C-A.~l 

\r 

Normal  Take  Siding       Continue  on          Enter  Siding        Proceed  on  Main 

Main  Track       at  First  Switch      Track  with  Caution 


P    R    R 


We  Lights 


853 

^No  Lights 


'5  No-glare  Lights 


\Lights 

Normal  Take  Siding  Normal  Take  Siding 

FIG.  9. — Take  siding  indicators,     (Pro.  R.  S.  A.  1918,  pages  276-277.) 


SIGNAL  INDICATIONS  17 

indication  it  swings  almost,  if  not  entirely,  clear  of  the  opening 
as  indicated  by  (c)  and  (d)  of  Fig.  8.  Just  above  each  disc  is  a 
light  for  the  night  indications  that  are  given  by  the  following 
colors:  (a)  red;  (b)  green;  (c)  white;  and  (d)  white.  Where  two 
discs  appear  on  one  mast,  the  upper  one  is  generally  the  home 
signal  and  the  lower  one  the  distant  signal. 


FIG.  10. — R.  S.  A.  take  siding  signal. 

10.  Take  Siding  Signal. — The  take  siding  signal  in  one  form  or 
another  is  used  by  a  few  roads  to  notify  trainmen  without  the  use 
of  train  orders  to  take  siding  at  non-interlocked  switches,  espe- 
cially located  at  some  distance  from  the  operating  towers.  The 
different  types  include  both  semaphore  arms  and  discs.  One  of 
the  forms  in  service  is  a  two-arm  signal  in  which  the  lower  arm  is 
2 


18 


RAILWAY  SIGNALING 


FIG.   11. — Ground  signals. 


FIG.  12.— Signal  bridge. 


SIGNAL  INDICATIONS 


19 


operated  to  the  45-degree  position  in  the  upper  quadrant  and  is 
marked  with  the  words  "  Take  Siding"  illuminated  at  night.  One 
road  employs  a  disc  case  that  displays  a  swinging  disc  for  day 
indications  and  a  blinking  light  for  night  indications.  Two 
roads  use  a  disc  bearing  a  white  letter  "S"  illuminated  at  night, 
and  two  use  a  yellow  disc  bearing  the  words  "Take  Siding" 
properly  illuminated  at  night.  Another  road  employs  five  no- 
glare  lights  arranged  in  the  form  of  an  X  for  both  day  and  night 


FIG.  13. — Bracket  signal. 

indications.  The  signal  is  located  in  the  rear  of  the  switch,  so 
that  the  engineman  must  pass  it  before  he  takes  the  siding.  It  is 
controlled  from  the  nearest  tower  or  from  the  train  despatched 
office,  and  is  usually  operated  by  means  of  the  ordinary  electric 
signal  mechanism. 

11.  Relative  Location  of  Signals  and  Tracks. — There  must  be  a 
set  of  signals  to  govern  the  movements  of  trains  in  each  direction. 
In  railway  practice  in  America,  ground  signals  are  nearly  always 
located  on  the  right-hand  side  of  the  track  they  govern,  as  indi- 


20 


RAILWAY  SIGNALING 


cated  by  Fig.  11.  On  one  or  two  double-track  roads  where  left- 
hand  running  is  the  custom,  they  are  located  on  the  left-hand  side. 
In  the  case  of  semaphore  signals,  on  steam  roads,  the  blade 
extends  to  the  right  of  the  post  while  on  electric  railways,  the 
blade  may  extend  either  to  the  right  or  to  the  left,  depending 
upon  local  conditions.  Where  there  are  several  parallel  tracks 
or  where  there  is  not  sufficient  room  at  the  side  for  semaphores, 
the  signals  are  usually  mounted  on  signal  bridges.  In  this  case, 


FIG.  14. — Bracket  signal  and  doll  post. 

they  are  mounted  on  short  poles,  supported  above  or  suspended 
below  the  bridge  directly  over  the  tracks  they  govern,  as  shown 
in  Fig.  12. 

Where  there  are  two  high-speed  tracks  for  traffic  in  the  same 
direction,  as  in  the  case  of  the  four-track  line,  the  bracket  signal 
may  be  used  as  shown  in  Fig.  13.  The  inside  signal  governs 
the  inside  track  of  the  two  and  the  outside  signal  the  outside 
track.  If  the  outside  track  is  a  freight  line  where  trains  are  run 


SIGNAL  INDICATIONS  21 

at  a  somewhat  lower  speed,  the  outside  pole  may  be  a  little  shorter 
than  the  inside  one. 

In  case  there  is  a  siding  between  the  high  signal  and  the  track 
it  governs,  the  bracket  type  of  semaphore  may  be  used  as  before. 
A  bracket  post  signal  will  govern  the  inside  track  and  a  short  doll 
pole  without  a  signal  blade  will  represent  the  outside  track. 
This  arrangement  is  simply  to  indicate  that  there  is  one  track 
between  the  signal  and  the  track  it  protects  as  shown  in  Fig.  14. 
A  purple  light  is  used  on  the  doll  pole  at  night.  If  there  are  two 
tracks  between  the  signal  and  the  track  it  governs,  two  such  doll 
poles  will  be  used  on  a  bracket  post. 


FIG.   15. — Upper  quadrant  two-position  dwarf  signal. 

Dwarf  signals  are  used  as  home  signals  to  give  interlocking 
indications  in  practically  the  same  manner  as  high  signals  ex- 
cept that  they  are  used  only  where  the  movements  of  trains  are 
slow.  The  dwarf  is  not  used  at  all  for  block  signaling  purposes, 
neither  is  it  used  as  a  distant  signal.  An  upper  quadrant  two- 
position  dwarf  signal  is  shown  in  Fig.  15.  It  is  the  practice  on 
many  roads  to  use  the  purple  instead  of  the  red  light  for  dwarf 
indications.  This  is  distinctive;  and,  although  of  short  range, 
it  is  possible  to  use  the  purple  since  the  train  movements  that 
it  governs  are  necessarily  slow. 


CHAPTER  III 
INTERLOCKING 

12.  Definition. — The  subject  of  signaling  naturally  divides  it- 
self into  two  phases,  interlocking  and  block  signaling.     As  dis- 
cussed here,  interlocking  is  the  operation  of  an  assemblage  of 
equipment  and  appliances  used  to  govern  the  movements  of 
trains  over  conflicting  routes;  while  block  signaling  is  the  opera- 
tion of  equipment  and  appliances  used  to  govern  the  movements 
of  following  or  opposing  trains  over  the  same  route. 

Where  movements  of  trains  on  one  track  may  conflict  with 
those  on  another,  such  movements  are  usually  governed  by  visi- 
ble signals  operated  by  an  interlocking  mechanism  so  constructed 
and  arranged  that  there  can  be  no  conflict  of  signal  indications. 
This  not  only  provides  safety  for  train  operation,  but  also  expe- 
dites train  movements.  Such  "an  arrangement  of  switches,  lock 
and  signal  appliances,  so  interconnected  or  interlocked  that  one 
movement  must  succeed  another  in  a  predetermined  order,"  is 
defined  by  the  American  Railroad  Association  as  an  interlocking 
plant. 

13.  Object. — The  plant  is  so  constructed  that  the  control  of 
all  the  ground  functions  is  located  at  one  point.     This  provides 
for  a  much  more  expeditious  operation  than  if  each  function  had 
to  be  manipulated  by  a  lever  on  the  ground.     The  control  equip- 
ment usually  is  placed  in  the  second  story  of  the  tower,  which  is 
so  located  and  constructed  as  to  permit  the  operator  to  see  the 
entire  yard.     Concentrating  the  controlling  apparatus  all  at  one 
point  provides  an  opportunity  for  interlocking  that  would  be 
almost  impossible  if  each  function  were  handled  as  a  separate 
unit. 

Up  to  1919  there  had  been  installed  approximately  5,300 
interlocking  plants  on  American  roads.  The  motives  that 
prompted  expenditures  for  such  equipment  were  based  on  the 
idea  of  expediting  train  movements  while  assuring  their  safety. 
At  a  railroad  crossing  where  no  interlocking  plant  is  installed, 
all  trains  in  most  states  are  obliged  by  law  to  come  to  a  full  stop 
before  they  attempt  to  pass  the  crossing.  The  purpose  of  such 
regulation  is  to  require  train  crews  to  ascertain  that  the  way  is 

22 


INTERLOCKING  23 

clear  in  order  to  prevent  collision,  and  even  then  there  is  a  strong 
possibility  of  trains  colliding.  If  there  should  be  a  number  of 
such  crossings  in  succession  in  regions  of  dense  traffic,  the  time 
lost  in  stopping  and  starting  would  tend  to  intensify  the  conges- 
tion that  might  arise  from  other  sources.  Where  interlocking 
plants  are  installed  at  crossings,  however,  trains  are  not  ordinarily 
required  to  stop.  This  affects  a  saving  not  only  in  the  time  ele- 
ment involved,  but  also  in  the  expense  of  operation  in  stopping 
and  starting  the  trains]  In  1905,  Mr.  J.  A.  Peabody,  Signal 
Engineer  for  the  Chicago  and  North  Western  Railway  Company, 
obtained  some  analyses  of  the  cost  of  starting  and  stopping 
trains;  and  from  the  data  then  available  he  determined  that  a 
road  could  economically  install  an  interlocking  plant  where  there 
were  between  16  and  20  trains  a  day.1  While  the  first  cost  of 
construction  and  the  expense  of  operation  of  such  plants  have 
increased  since  that  time,  the  expense  of  train  service  and  equip- 
ment has  increased  in  proportion  so  that  the  conclusions  drawn 
probably  still  hold  true. 

In  the  case  of  four-track  lines  where  two  tracks  are  ordinarily 
given  to  passenger  service  and  two  to  freight,  the  capacity  of  the 
road  may  be  considerably  increased  if  the  crossovers  between 
tracks  having  traffic  in  the  same  direction  are  interlocked.  This 
arrangement  would  permit  a  fast  freight,  for  instance,  safely  to 
take  the  passenger  track  between  two  points  in  order  to  pass  a 
slower  freight  without  the  necessity  of  the  slower  train  taking 
siding  and  waiting. 

14.  General  Plan. — The  first  step  in  installing  an  interlocking 
plant  is  to  make,  or  otherwise  secure,  a  plan  of  the  tracks  affected. 
This  should  be  drawn  to  suitable  scale  and  should  show  all  tracks, 
switches,  and  railroad  crossings,  and  all  street  crossings,  buildings, 
tanks  and  water-cranes  that  may  influence  the  details  of  the 
plant.  The  size  of  the  scale  will  depend  upon  the  complications 
and  local  conditions,  and  will  usually  be  100  ft.  to  the  inch.  Fifty 
feet  to  the  inch  may  be  chosen  if  greater  detail  is  necessary. 
The  tower,  signals,  derails,  and  other  parts  of  the  interlocking 
plant  are  then  located  on  the  map  using  for  this  purpose  the  sym- 
bols adopted  and  recommended  by  the  Railway  Signal  Associa- 
tion, and  which  are  shown  in  Appendix  B.  It  will  be  noted  that  a 
signal  is  laid  flat  on  the  map  with  the  top  in  advance  of  the  base 
as  the  train  it  governs  approaches  it. 

1  Proceedings  Railway  Signal  Association,  Volume  I. 


24  RAILWAY  SIGNALING 

Two  sets  of  signals  are  required  for  an  interlocking  plant,  a 
home  signal  and  a  distant  signal.  The  home  signal  stands  just  in 
the  rear  of  the  derail  or  switch  that  it  governs;  while  the  distant 
signal  stands  from  1,200  to  6,000  ft.  in  the  rear  of  the  home 
signal.  The  distance  between  the  two  signals  depends  upon  the 
length  of  track  required  to  stop  a  train  and  the  kind  of  power  used 
to  operate  the  distant  signal.  The  home  signal  is  the  controlling 
one  and  must  not  be  passed  by  a  train  until  the  proper  indication 
is  given.  The  distant  signal  is  a  purely  cautionary  function  and 
serves  to  warn  enginemen  of  the  indication  that  its  home  signal 
is  showing  at  that  particular  time. 

On  account  of  the  heavier  train  equipment  and  the  high 
speed  found  necessary  to  maintain  schedules,  many  roads  that 
formerly  operated  their  distant  signals  mechanically  with  a  wire 
have  moved  them  farther  away  from  the  home  signal  and  are 
operating  them  by  electric  power.  This  increased  distance 
affords  greater  safety  in  train  operation  wjth  but  little,  if  any, 
more  expense  for  maintenance.  From  a  questionnaire  sent  out 
by  the  Railway  Signal  Association  in  1906  it  was  found  that  for 
15  roads,  approximately  one-third  of  the  mileage  in  the  United 
States,  the  average  distance  from  the  distant  signal  to  the  home 
signal  was  3,745  ft.  and  to  the  interlocking  tower  was  4,025  ft. 
In  1901  the  average  distance  from  the  distant  signal  to  the  home 
signal  was  1,444  ft.  and  to  the  tower  was  1,750  ft. 

In  addition  to  signals,  derails  also  form  a  very  necessary  part  of 
the  interlocking  equipment  at  railroad  crossings  and  junctions. 
A  derail  is  a  device  for  throwing  an  engine  or  car  from  the  track ; 
and  the  presence  of  such  equipment  in  the  plant  is  to  guarantee 
that  the  train  shall  stop  before  it  reaches  the  crossing  should  the 
route  not  be  lined  up  for  it  to  proceed.  The  derail  is  generally 
located  about  500  ft.  from  the  crossing,  while  the  home  signal  is 
placed  about  58  ft.  in  the  rear  of  the  derail,  as  shown  in  Fig.  16. 
By  placing  the  derail  this  distance  from  the  crossing  there  is 
practically  no  chance  for  the  derailed  train  to  continue  on  the  ties 
and  reach  the  crossing. 

All  signals  and  derails  at  an  interlocked  crossing  stand  nor- 
mally at  danger  to  stop  traffic.  When  they  are  set  against  move- 
ment of  traffic,  they  are  said  to  be  "normal;"  when  they  are  in 
position  for  movement  of  traffic,  they  are  said  to  be  " reversed." 
The  levers  corresponding  to  these  positions  are  also  normal  and 
reversed.  Usually  one  lever  is  assigned  to  operate  each  function. 


INTERLOCKING 


25 


15.  General  Order  of  Locking  Signals  and  Derails. — When  a 
movement  over  a  crossing  is  desired,  the  towerman  first  closes 
the  two  derails  on  the  track,  then  he  clears  the  home  signal  on  the 
side  Som  which  the  train  is  approaching,  and  finally  he  clears  the 
distant  signal  on  that  side.  When  a  derail  on  one  track  of  a 
crossing  is  reversed,  it  locks  the  derails  of  the  conflicting  tracks 
at  normal.  When  the  derails  are  reversed  the  home  signal  may 
then  be  reversed,  and  this  movement  locks  the  derails  reversed. 
The  distant  signal  is  then  unlocked  and  may  be  reversed,  locking 
the  home  signal  clear  or  reversed.  The  levers  in  the  tower  must 


VfKfBt 

LOCKS 

RQgxn 

LOCKS 

1 

<f> 

3 

Spore  Space 

2 

1  .*  'S 

10 

&/B 

3 

I 

II 

5pare  Space 

4 

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StMrrvSpoce 

13 

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6 

8,12 

14 

1 

7 

SpareSpace 

IS 

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16 

V 

FIG.   16. — Single  track  crossing  a  single  track. 

be  operated  in  this  order,  for  the  construction  of  the  plant  will 
permit  no  other.  To  put  the  plant  normal  the  functions  must  be 
operated  in  the  opposite  order. 

To  have  a  train  pass  from  A  to  B  in  Fig.  J^,  the  towerman 
clears  derails  6  and  10.  This  locks  derailsjg^lnd  12  open.  He 
then  clears  the  home  signal  2,  which  locks  6  and  10  closed,  and 
13  normal.  He  finally  clears  distant  signal  1,  which  locks  2 
clear.  To  set  the  track  to  normal  again  the  towerman  sets 
distant  signal  1  to  caution,  then  home  signal  2  to  the  stop 
position,  and  finally  opens  derails  6  and  10. 

In  order  to  line  up  a  route  through  an  interlocking  plant,  there- 
fore, all  the  derails  on  the  route  must  be  reversed,  locking  those 


26  RAILWAY  SIGNALING 

on  conflicting  routes  normal.  Clearing  the  home  signal  then 
locks  all  the  derails  in  the  route  reversed  and  all  opposing  direc- 
tion signals  normal.  Finally,  clearing  the  distant  signal  locks 
the  home  signal  reversed. 

16.  Locking  Sheet. — A  locking  sheet  is  a  tabulated  statement 
of  the  order  in  which  the  levers  of  any  particular  plant  interlock 
one  another.  In  the  locking  sheet  shown  in  connection  with  Fig. 
16,  the  levers  in  the  first  column  are  all  understood  to  be  reversed. 
Those  in  the  second  column  that  are  reversed  are  shown  as  such 
by  drawing  a  circle  around  them ;  otherwise  they  are  understood 
to  be  normal.  The  chart  reads: 

Lever  1  reversed  locks  lever  2  reversed; 

Lever  2  reversed  locks  levers  6  and  10  reversed  and  13  normal: 
and  so  on  to  the  bottom. 

The  numbers  on  the  functions  correspond  to  the  numbers  on 
the  levers  in  the  tower;  and  since  interlocking  machines  are 
built  with  lever  spaces  in  multiples  of  four,  it  is  well  to  distribute 
the  extra  spaces  through  the  middle  of  the  machine  for  additional 
levers  that  may  be  added  later. 


REVERSED 


LOCKS 


©       W     (7) 


LEVER 

WHEM 

LOCKS 

s 

(z) 

@ 

FIG.   17. — Form  of  sheet  for  special  locking. 

If  there  are  levers  that  operate  special  locking,  the  sheet  must 
include  them  also.  The  usual  form  of  expressing  such  lock- 
ing is  as  shown  in  one  of  the  forms  in  Fig.  17,  which  in  each 
case  reads  lever  5  reversed  locks  4  reversed  when  7  is  reversed. 

When  facing  point  locks,  designated  F.P.L.,  are  used  to  lock 
the  derails  and  switches,  the  two  locks  on  the  same  route  at  a 
crossing  are  generally  thrown  by  one  lever  and  the  two  derails  by 
another.  In  the  case  of  switch  and  lock  movements,  designated 
S.L.M.,  one  lever  in  a  mechanical  plant  is  generally  assigned  to 
each  derail  or  switch,  although  two  may  be  assigned  where  power 
is  used. 

If  facing  point  locks  were  used  in  Fig.  16,  the  numbering  and 
locking  would  be  as  shown  in  Fig.  18.  A  single  track  crossing  a 
double  track  where  switch  and  lock  movements  are  used,  has  a 
locking  sheet  as  shown  in  Fig.  19.  Back-up  movements,  or 


INTERLOCKING 


27 


those  that  run  counterwise  to  the  normal  direction  of  traffic,  are 
governed  by  dwarf  signals.     Otherwise  the  installation  is  the 


LOCKING  SHEET 


REVfKSf 

LOCKS 

WFRSf 

LOCHS 

1 

9 

® 

2 

13 

10 

Spare 

3 

$ 

II 

7 

4 

®  & 

12 

Spare 

S 

Span? 

13 

®  2 

6 

i 

M 

7 

a 

IS 

4 

8 

Spare 

16 

FIG.   18. — Facing  point  locks. 


FIG.  19. — Single  track  crossing  a  double  track. 

same  as  for  a  single-track  crossing.     The  derails  for  the  dwarf 
signals  are  generally  located  about  250  to  300  ft.  from  the  crossing. 


28 


RAILWAY  SIGNALING 


17.  Diverging  Routes. — There  are  many  cases  of  diverging 
routes  that  require  more  than  one  signal  on  a  post.  In  some 
instances  the  diverging  routes  are  high-speed  lines  and  in  others 
they  are  low-speed  lines.  Where  two  high-speed  lines  diverge 


A 


t/O 


•*•/ 


LOCKING  SHEET 


REVERSE 

LOCKS 

REVERSE 

LOCKS 

1 

9 

7 

6,£ 

2 

®®  // 

8 

Spare 

3 

SO)  9 

9 

J® 

4 

Spcrrs 

10 

® 

S 

II 

2  © 

€ 

7® 

12 

© 

c 


FIG.  20. — High  speed  diverging  routes. 


there  is  a  home  signal  and  sometimes  a  distant  signal  for  each 
route,  although  generally  there  is  only  one  distant  signal.  Fig- 
ure 20  shows  an  arrangement  for  two  high-speed  diverging  routes. 
The  upper  blade  of  the  two-arm  signal  governs  the  superior  route, 


LOCKIHGSHEET 


FIG.  21. — Single  track'  and  turnout. 

which  is  usually  the  straight  one,  while  the  lower  blade  governs 
the  inferior  route,  which  is  generally  the  diverging  one.  In  the 
Railway  Signal  Association  standard  the  lower  blade  stands  22 
ft.  6  in.  above  the  foundation  and  the  upper  one  7  ft.  higher. 


FIG.  22. — Single  track  and  two  low  speed  diverging  routes. 

Whenever  a  very  low-speed  route  diverges  from  a  main  line, 
the  high-speed  route  may  be  governed  by  a  high  signal,  while  the 
inferior  route  may  be  governed  by  a  dwarf  signal  placed  either 
on  the  lower  portion  of  the  high  signal  post  or  on  the  ground  at  the 


INTERLOCKING 


29 


• 

base  of  the  post.  Figure  21  shows  an  arrangement  where  the 
two  blades  are  on  the  same  post.  When  the  dwarf  signal  is 
cleared,  the  high-speed  home  and  distant  signals  are  respectively 
in  the  stop  and  caution  positions.  The  inferior  or  low-speed 
route  may  be  a  cross-over,  a  transfer,  or  a  spur.  The  dwarf 


FIG.  23. — Trailing  point  crossover. 

signal  on  the  siding  is  to  govern  trains  moving  from  the  siding  to 
the  main  track. 

Where  there  are  two  or  more  inferior  routes  diverging  within 
a  comparatively  short  distance,  the  common  practice  is  to  have  a 
set  of  high  signals  to  govern  the  main  line  and  a  dwarf  all  of  the 


FIG.  24. — Single  track  crossing  and  high  speed  diverging  route. 

others.  In  Fig.  22  the  dwarf  may  govern  either  of  the  diverging 
routes.  It  will  show  a  clear  indication  when  any  of  the  diverging 
routes  is  lined  up. 

As  the  dwarf  signal  is  low,  the  engineman  can  see  it  only  a 
short  distance  ahead  and  therefore  he  is  required  to  reduce  his 


30  RAILWAY  SIGNALING 

speed  and  to  keep  his  locomotive  under  control  as  he  approaches 
the  turnout.  On  the  other  hand,  the  blade  must  be  high  in  the 
case  of  high-speed  routes  in  order  that  the  engineman  may  see 
it  at  a  distance.  Besides  requiring  the  engineman  to  check  his 
speed,  the  dwarf  signal  has  two  other  advantages:  (1)  that  it  is 


FIG.  25. — Single  track  crossing  and  transfer  track. 

much  cheaper  than  the  high  signal;  (2)  that  it  can  always  be 
placed  next  to  the  track  it  governs,  even  between  tracks  if 
necessary. 

Figures  23  to  26  inclusive  illustrate  additional  cases  of  route 
signaling. 

_"" 


FIG.  26. — Double  track  diverging  routes. 

18.  Movable  Bridge  Interlocking. — Viewed  from  the  standpoint 
of  train  movements,  the  question  of  horizontal  and  vertical  align- 
ment of  the  track  at  each  end  of  the  bridge  is  the  most  serious 
that  comes  up  in  connection  with  drawbridge  operation.  The 
bridge  when  properly  closed  not  only  must  be  so  placed  that  the 
track  centers  are  continuous,  but  also  it  must  be  so  seated  that 
the  top  of  the  rail  is  continuous.  For  this  purpose  end  lifts  are 
required  for  horizontal  swing  bridges  to  place  the  rails  to  the 
proper  surface  and  locks  to  secure  them  in  this  position  and  also 
in  proper  alignment.  Locks  are  necessary  also  for  lift  bridges  in 
order  to  secure  the  continuity  of  the  track. 


INTERLOCKING 


31 


The  rail  ends  may  be  cut  either  mitered  or  square.  In  case  of 
mitered  joints  the  full  thickness  of  the  web  of  the  rail  should 
continue  to  the  end  of  the  point.  The  point  should  be  placed  in 
a  trailing  position  at  each  end  of  the  bridge  on  double  track  and 
in  a  trailing  position  towards  the  center  of  the  bridge  on  single 
track.  Some  sort  of  provision  should  be  made,  as  for  instance 
the  addition  of  an  easer  rail  on  the  outside  of  the  joints,  to  support 
the  train  wheels  across  the  gap  between  the  bridge  rails  and  the 
approach  rails. 

Signals  are  used  to  protect  movable  bridges  in  practically  the 
same  manner  as  railway  crossings.  The  interlocking  machine  is 
frequently  placed  on  the  bridge  itself.  The  interlocking  should 
be  so  constructed  that  the  bridge  should  be  locked  in  alignment 
for  traffic  before  the  signals  can  be  cleared;  and  conversely,  the 


5  -Bridge  Coupler 
6-  Bridge  Lock 
7  -Engine  Lock 
LOCKING  SHEET 

VEYERSE 

LOCKS 

REVERSE 

LOCKS 

1 

® 

7 

2 

®  ©// 

8 

5pare 

3 

®  ® 

9 

© 

4 

© 

10 

@  ® 

s 

© 

II 

®  ®^ 

6 

© 

12 

® 

FIG.  27. — Drawbridge  interlocking. 

signals  should  all  be  locked  at  the  stop  position  when  the  bridge 
is  open.  Where  mechanical  interlocking  is  employed  the  con- 
nections between  the  pipes  on  the  bridge  and  those  on  the  roadbed 
are  made  by  means  of  couplers.  The  order  in  which  the  tower- 
man  operates  the  functions  to  close  a  bridge  and  line  up  the 
route  for  trains  is:  motor,  bridge  locks,  couplers,  derails,  facing 
point  locks,  home  signal,  and  distant  signal.  Each  one  reversed 
locks  all  those  in  front  of  it  reversed.  There  is,  then,  no  possi- 
bility of  opening  the  bridge  until  every  signal  and  derail  is  set  at 
the  stop  indication.  In  order  to  open  the  bridge  the  levers  must 
be  placed  normal  in  exactly  the  reverse  order.  Figure  27  gives 
a  plan  of  the  signal  and  derail  arrangement  together  with  a  lock- 
ing sheet  for  a  single-track  swing  bridge.  The  derails  are  placed 
at  least  500  ft.  from  the  bridge  so  that  the  derailed  trains  cannot 


32  RAILWAY  SIGNALING 

run  into  the  stream.  Usually  each  derail  and  facing  point  lock 
has  its  own  lever  to  guarantee  safety  in  operation.  In  the  case  of 
double-track  lines  the  derails  for  back-up  movements  should  be 
not  less  than  300  ft.  from  the  bridge. 


Hi    U    Illl 

FIG.  28. — Drawbridge  interlocking. 

19.  Requirements  for  the  protection  of  traffic  at  movable 
bridges  as  defined  in  the  Proceedings  of  the  Railway  Signal 
Association  in  1916: 

The  protective  appliances  at  drawbridges  consist  in  devices  for  insur- 
ing that  the  bridge  is  in  proper  position,  and  the  track  in  condition  for 
the  passage  of  trains  over  draw,  or  for  reduction  to  a  minimum  of  the 
damage  in  case  of  trains  not  stopping  when  track  is  not  in  condition 
for  passage  of  same  over  draw;  also  the  usual  devices  for  protection 
against  damage  in  case  of  derailment. 

The  protective  devices  may  be  classified  under  the  headings: 

(a)  Interlocking  power  and  bridge  devices. 

(ft)  Bridge  surfacing,  aligning  and  fastening  devices. 

(c)  Rail-end  connections. 

(d)  Signaling  and  interlocking. 

(e)  Guard  rails. 

(a)  Interlocking  Power  and  Bridge  Devices. — Interlocking  the  draw- 
bridge devices  so  that  their  movements  must  follow  in  a  predetermined 
order  to  protect  the  drawbridge  machinery. 

(b)  Bridge  Surfacing,  Aligning  and  Fastening  Devices. — Drawbridges 
should  be  equipped  with  proper  mechanism  to  surface  and  align  them 
accurately  and  fasten  them  securely  in  position.     This  condition  can 
be  secured  by  the  use  of  efficient  end  lifts  in  case  of  swing  bridges,  and 
by  proper  end  locks  in  case  of  lift  bridges. 

(c)  Rail-end  Connections. — Rail  ends  may  be  mitered  or  cut  square. 
Mitered  rails  where  lapped  should  retain  the  full  thickness  of  the  web 
to  the  points.     The  points  should  be  trailing  to  normal  traffic  where 
possible;  on  single-track  bridges  the  points  should  be  trailing  to  traffic 
entering  the  movable  span. 

Where  rail  ends  are  cut  square  or  mitered  and  not  lapped,  they  should 
be  connected  by  sliding  sleeve  or  joint  bar  or  by  easer  rails  to  carry  the 
wheels  over  the  opening  between  the  end  of  bridge  and  approach  rails. 


INTERLOCKING 


33 


(d)  Signaling  and  Interlocking* — If  trains  are  to  proceed  over  draw- 
bridges which  are  in  service,  without  first  stopping,  interlocking  should 
be  installed  which  will  provide  that  the  drawspan,  tracks  and  switches 
within  the  limits  of  the  plant  are  locked  in  the  proper  position. 

This  will  require: 

1.  Locking  drawbridge  devices. 

2.  Locking  providing  for  the  proper  order  of  operation  of  signaling 
devices,  such  as  signals,  switches  and  derails. 

This  interlocking  will  require  the  following  order  of  operation: 


BEFORE   OPENING   A   DRAWBRIDGE 


1.  Display  stop  signals. 

2.  Unlock  rail  and  bridge  devices. 


BEFORE  OPERATING  TRAINS  OVER 
DRAWBRIDGE 

1.  Lock  bridge  and   rail  devices. 

2.  Display  clear  signals. 


Since  there  are  various  types  and  designs  of  drawbridges  and  various 
drawbridge  devices  for  each  of  the  types,  and  also  various  designs  and 
types  of  signaling  devices,  as  well  as  various  locations,  from  which  they 
all  may  be  interlocked  and  operated,  a  typical  example  only  of  the  detail 
order  of  operations  is  given;  viz.,  a  swingbridge  with  all  its  devices 
operated  from  one  location  on  the  drawspan,  having  home  and  distant 
signals,  derails,  etc. 


To  OPEN  DRAWBRIDGE 

1.  Display  stop  signals. 

2.  Unlock  derails. 

3.  Open  derails. 

4.  Uncouple    interlocking    connec- 

tions. 


5.  Unlock  rail-end  connections. 


6.  Unlock  bridge  surfacing,  aligning 

and  fastening  devices. 

7.  Operate    power-controlling    de- 

vice to  position  permitting  ap- 
plication of  power  to  bridge 
machinery. 

8.  Withdraw  rail-end  connections. 

9.  Withdraw      bridge      surfacing, 

aligning  and  fastening  devices. 
10.  Open  bridge. 


To  PASS  TRAINS  OVER    DRAWBRIDGE 

1.  Close  bridge. 

2.  Insert  bridge  surfacing,  aligning 

and  fastening  devices. 

3.  Insert  rail-end  connections. 

4.  Operate  power-controlling  device 

to  position  preventing  applica- 
tion of  power  to  bridge  ma- 
chinery. 

5.  Lock  bridge  surfacing,  aligning 

and  fastening  devices. 

6.  Lock  rail-end  connections. 


7.  Couple  interlocking  connections. 


8.  Close  derails. 

9.  Lock  derails. 

10.  Display  clear  signals. 


34 


RAILWAY  SIGNALING 


Derails. — The  above  example  of  order  of  operation  includes  derailing 
switches,  but  their  use  is  not  recommended  in  all  cases.  Each  situation 
must  be  given  special  study  with  respect  to  (a)  the  use  of  derails,  smash 


boards  or  similar  devices;  (6)  their  location  with  respect  to  drawspan; 
and  (c)  the  use  and  length  of  guard  rails. 

(e)  Guard  Rails. — Guard  rails  should  be  provided  as  for  fixed  bridges, 
except  for  the  necessary  breaks  at  the  ends  of  the  movable  span.    Ob- 


INTERLOCKING  35 

struction  to  derailed  wheels  which  are  guided  by  the  guard  rails  should 
be  reduced  to  a  minimum. 

(/)  Rail  Attachments. — The  rails  and  attachments  should  be  separated 
from  the  metallic  structure  so  track  circuits  may  be  successfully  operated 
the  entire  length  of  the  bridge. 

(g)  Bridge  Devices. — The  various  bridge  devices  should  be  so  designed 
that  Railway  Signal  Association  interlocking  apparatus  may  be  used. 

(h)  Locking. — Electric  and  time  locking  are  regarded  as  adjuncts. 

20.  Track  Diagram  and  Manipulation  Chart. — A  track  dia- 
gram and  a  manipulation  chart  are  usually  placed  in  each  tower 
for  the  benefit  of  the  signalmen.  The  track  diagram  is  a  plan  of 
the  track  layout  showing  the  relative  positions  of  the  switches, 
derails,  and  signals  with  the  number  assigned  to  each  that 
corresponds  to  the  lever  that  operates  it;  the  manipulation  chart 
shows  the  order  in  which  these  functions  must  be  operated  to 
line  up  a  certain  route.  The  diagram  and  chart  are  made  on 
rather  a  large  scale  and  are  hung  on  the  front  wall  of  the  tower  so 
that  the  signalmen  can  see  them  as  they  stand  to  manipulate 
the  levers.  A  typical  track  diagram  and  manipulation  chart 
are  illustrated  in  Fig.  29. 


CHAPTER  IV 
MECHANICAL  INTERLOCKING 

INTERLOCKING  MACHINES 

21.  General. — Two  kinds  of  interlocking  plants  are  built— 
mechanical  and  power.     In  the  mechanical  plant,  the  levers  are 
operated  by  hand;  and  the  movements  are  transmitted  by  hand 
power  to  the  switches,  signals,  and  derails  by  means  of  pipes, 
wires  and  other  mechanical  appliances.     In  the  other  type  the 
levers  are  operated  by  hand,  but  they  are  so  constructed  as  to 
bring  into  action  some  kind  of  power  to  operate  the  switches, 
signals,  and  derails.     The  power  most  commonly  used  is  air  or 
electricity,  or  a  combination  of  the  two;  and  such  plants  are 
known  as  pneumatic,  electric,  or  electro-pneumatic. 

The  levers  of  an  interlocking  plant  are  arranged  in  a  row  across 
the  second  floor  of  an  interlocking  tower  parallel  to  one  set  of 
tracks  in  the  plan.  The  front  of  the  interlocking  machine  is  the 
side  on  which  the  towerman  stands  while  he  operates  the  levers. 
The  levers  are  numbered  from  the  left  to  the  right  of  the  tower- 
man as  he  stands  in  position  to  operate  his  machine.  The 
location  of  the  levers  in  the  machine  should  correspond  somewhat 
to  the  respective  locations  of  the  functions  on  the  ground.  In 
the  case  of  the  railroad  crossing,  those  signal  levers  that  stand 
nearest  together  on  the  ground  should  be  grouped  nearest 
together  in  the  machine.  Usually  the  signal  levers  are  on  the 
ends  and  the  switches  and  derails  between.  The  arrangement 
of  the  levers  should  be  such  as  to  cause  the  signalman  to  walk 
back  and  forth  as  little  as  possible  to  manipulate  them. 

The  mechanical  machines  may  have  either  horizontal  or 
vertical  locking.  The  horizontal  type  is  known  as  Saxby  and' 
Farmer;  the  vertical  has  three  similar  designs,  Standard  or  Style 
A,  Johnson,  and  National.  Most  of  t'he  vertical  locking  plants 
in  use  have  Style  A  machines. 

22.  Horizontal  Locking. — Figure  30  illustrates  an  eight-lever 
Saxby  and  Farmer  interlocking  machine,  while  Fig.  31  shows  it 
more  in  detail.     The  figures  used  in  the  explanation  of  the  system 

36 


MECHANICAL  INTERLOCKING 


37 


FIG.  30. — Saxby  and  Farmer  interlocking  machine. 


LEVER 

LOCKING  SHAFT 
LOCKING  BRACKET 
LOCKING  BAR 
ROCKER  LINK 


FIG.  31. — Saxby  and  Farmer  interlocking  machine. 


38 


RAILWAY  SIGNALING 


of  horizontal  locking  refer  to  the  sketch  in  Fig.  32.  Lever  1 
is  pivoted  near  its  lower  end  at  3  and  is  shown  in  the  sketch  in 
its  normal  position.  Rocker-link  5  is  pivoted  at  its  center  4. 
The  back  end  of  this  rocker-link  is  connected  by  means  of  the 
universal  link  6  to  the  locking  shaft  crank  7,  which  in  turn  is 
rigidly  fastened  to  the  locking  shaft  9.  Horizontal  locking  bar 
10a  is  connected  to  locking  shaft  9  by  means  of  the  locking  bar 
driver  8.  As  the  towerman  pulls  on  latch  2  of  lever  1,  he  lifts  for 


FIG.  32. — Saxby  and  Farmer  locking. 

one-half  its  throw,  the  back  end  of  rocker-link  5.  This  movement 
is  transmitted  to  bar  10a  which  is  thus  driven  half  its  throw. 
The  dog  riveted  on  top  of  bar  10a  makes  miter  contact  with  cross- 
lock  11,  and  the  half  throw  of  bar  10a  gives  full  throw  to  11, 
making  contact  with  the  dog  on  the  other  horizontal  locking  bar 
106  and  locking  it  in  its  normal  position. 

The  lever  is  then  thrown  over  to  the  opposite  end  of  the  rocker- 
link  as  shown  in  Fig.  33;  and  as  the  latch  is  released  and  comes 
into  proper  position,  it  imparts  the  other  half  of  the  movement  to 
the  horizontal  locking  bar.  While  the  movements  of  the  signals 


MECHANICAL  INTERLOCKING 


39 


and  switches  are  made  by  the  lever,  the  movements  of  the  locking 
are  all  made  by  the  latch.  This  is  known  as  preliminary  or  latch 
locking,  and  is  very  fundamental  in  the  construction  and  opera- 
tion of  the  machine.  This  insures  that  not  only  must  the  lever  be 
placed  in  its  full  normal  or  reverse  position,  but  that  it  also 
must  be  locked  in  this  position  before  any  other  levers  can  be 
unlocked.  Furthermore,  with  this  arrangement  the  signalman 
can  apply  only  a  comparatively  small 
amount  of  pressure  against  the  lock- 
ing bed;  whereas,  if  the  lever,  itself, 
were  connected  directly  to  the  lock- 
ing he  might  be  able  to  apply  enough 
force  to  cause  the  locking  to  break 
or  fail. 

The  locking  shafts,  locking  bars, 
dogs,  cross-locks,  and  brackets 
assembled  in  working  order  con- 
stitute what  is  called  the  locking 
bed.  The  locking  bars  are  H  by  % 
in.  in  section  and  are  arranged  in 
pairs.  The  pairs  have  %  in.  clear 
space  between  them.  Most  of  the 
machines  are  constructed  with  half 
as  many  brackets  as  levers  and  they 
are  spaced  to  come  between  the  lock- 
ing shafts  and  not  directly  above 
them.  The  cross-locks  may  extend 
between  two  locking  bars  or  entirely 
across  the  bed  depending  upon  the 
particular  locking  construction.  The 
square  in  section  and  have  a  throw  of 


FIG.    33. — Saxby  and  Farmer 
interlocking  machine. 


cross-locks    are  %  in. 
in.     When  the  lever  is 

normal,  the  locking  bar  stands  as  far  to  the  right  as  it  is  possible 
to  go  ;  when  the  lever  is  reversed,  the  bar  stands  as  far  to  the  left 
as  it  is  possible  to  go,  moving  from  one  position  to  another 
through  a  distance  of  1%  in. 

23.  Special  Locking.  —  Special  locking  is  applied  to  the  Saxby 
and  Farmer  machine  by  having  a  long  crooked  dog  fastened  to  the 
locking  bar  in  such  a  manner  as  to  permit  it  to  swing  about  one 
end.  This  is  called  a  swing  dog  or  "when"  dog.  The  cross-lock 
is  made  in  two  pieces,  one  on  each  side  of  the  swing  dog.  The  dog 
on  one  locking  bar  will  drive  the  cross-lock  to  engage  another 


40  RAILWAY  SIGNALING 

when  the  swing  dog  is  in  place  between  the  two  sections  of  the 
cross-lock.  That  is,  dog  1  reversed  will  lock  2  normal  when 
swing  dog  4  is  reversed.  When  4  is  reversed  it  makes  the  cross- 
lock  practically  continuous,  for  4  can  swing  about  its  pivot  P, 
Fig.  34.  If  4  is  not  reversed,  reversing  1  will  have  no  effect  on  2. 
Figure  35  shows  the  different  forms  of  dogs  used  in  the  Saxby  and 

I ^    Farmer  machines.     Numbers 

1  to  13  inclusive  are  locking 
dogs;  14,  16,  and  18  are  left- 
hand  swing  dogs;  15,  17,  and 
19  are  right-hand  swing  dogs; 


v 


— >      \ 

TH  IJ   20  is  a  swing  dog  trunnion; 

FIG.  34.-Special  horizontal  locking.      ^    ^    &    locking    bar    driver; 

32,  33,  and  34  are  stock  pieces  for  making  locking  bars  and 
cross-locks. 

24.  Vertical  Locking. — In  the  case  of  machines  with  the  vertical 
type  of  locking,  the  locking  bed  stands  vertically;  whence  the 
name,  vertical  locking.  The  levers  are  substantially  the  same  as 
in  the  Saxby  and  Farmer  machines  and  they  operate  rocker-links 
in  practically  the  same  manner,  but  the  remainder  of  the  con- 
struction is  very  different.  Figure  36  shows  a  view  of  the  Style  A 
machine,  while  Fig.  37  gives  more  details  of  the  construction. 
The  end  of  the  rocker-link  is  connected  by  a  link  to  a  tappet 
bar,  which  it  slides  up  and  down  through  a  distance  of  1^6  in. 
On  the  sides  of  the  tappet  are  V-shaped  notches  and  on  the  front 
are  tappet  pieces  that  engage  dogs  fastened  to  small  locking  bars 
which  slide  horizontally  through  locking  guides.  Two  or  more 
dogs  are  fastened  to  each  bar,  and  as  the  tappet  is  pushed  or 
pulled  it  impinges  the  dog  by  miter  contact.  If  the  bar  is  free  to 
move,  the  lever  may  be  thrown.  The  sliding  of  the  bar  will  cause 
one  or  more  dogs  on  it  to  engage  the  notches  of  other  tappets, 
locking  them  in  either  the  normal  or  reverse  position.  The  lock- 
ing bars  are  %  in.  in  section  and  have  a  throw  of  %Q  in.  Lifting 
the  latch  in  the  vertical  machine  gives  the  rocker-link  and  the 
tappet  one-half  their  throw,  and  releasing  it  at  the  other  end  of 
the  quadrant  completes  the  locking. 

Vertical  machines  are  ordinarily  built  with  not  more  than 
four  locking  plates,  which  are  numbered  from  the  top  down,  1,  2, 
3,  and  4.  The  plates  are  made  to  contain  both  back  and  front 
locking  bars.  Three  bars  may  be  placed  side  by  side  in  the  back 
of  each  locking  plate  and  five  in  front,  giving  a  maximum  of  eight 


MECHANICAL  INTERLOCKING 


41 


bars  to  each  plate.  The  back  locking  dogs  operate  in  the  same 
plane  as  the  tappet  bars.  If  it  should  become  necessary  at  any 
time  to  install  more  locking  bars,  additional  locking  plates  may  be 


-liF- 


15 


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20 


noon 


24 


17 


21 


23 


i        i     i          i     Q        i     \\          i     []          i     []  i    <]  i 

25        26         27         28          29  3O  31 


22 


rtfi- 


32 


METHOD   OF   SPLICING   BARS 


33 


n- 


34 

FIG.  35. — Locking  details  of  Saxby  and  Farmer  interlocking  machine. 

provided  by  using  extension  legs  for  the  machine.     In  making 
up  a  dog  chart,  the  back  locking  for  each  space  is  shown  above 


42 


RAILWAY  SIGNALING 


the  front  locking  of  that  space.  Figure  38  illustrates  an  example 
of  back  locking.  1  and  2  are  tappet  bars  so  arranged  that  1  re- 
versed locks  2  normal. 

25.  Special  Locking. — The  swing  dog  in  the  vertical  locking 
machine  is  constructed  somewhat  differently  from  that  in  the 
Saxby  and  Farmer  machine.  The  dog  is  fastened  to  tappet  4  in 


FIG.  36. — Style  A  interlocking  machine. 

Fig.  39  and  swings  in  a  vertical  plane  between  the  adjacent  dogs  a 
and  6.  The  special  locking  is  in  the  plane  of  the  front  locking 
bars.  In  the  figure,  5  reversed  locks  1  and  2  normal  when  4  is 
reversed.  If  4  is  not  reversed,  however,  reversing  5  has  no 
effect  on  1  and  2. 

In  Fig.  40,  the  numbers  1  to  36  inclusive  represent  front 
locking  dogs;  37  to  39  are  front  couplings;  40  to  42  are  front 
carriers;  43  is  a  special  swing  dog;  44  to  49  are  tappet  pieces; 


MECHANICAL  INTERLOCKING 


43 


FIG.  37. — Style  A  interlocking  machine. 


1 

^ 

-"-4 

:&"j$2 

y  — 

,1 

i 

FIG.  38.— Back  locking. 


FIG.  39. — Special  vertical  locking. 


44 


RAILWAY  SIGNALING 


50  to  65  are  back  locking  dogs;  66  and  67  are  back  couplings; 
68  to  71  are  back  carriers;  72  to  77  are  front  locking  dogs;  and 
83  is  a  short  piece  of  steel  locking  bar. 


13  14  IS  16  17 


Q 


31  38  33  34  35  36 


a  a 

31  38 

D  0  0  SB 

40  41  48  43 


44  45  46  47  46 


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63  64 


61 

D  a 

66  67  68  68          70          71 


79 


FIG.  40.  —  Locking  details  of  style  A  interlocking  machine. 

26.  The  Dog  Chart.  —  The  dog  chart  is  a  plan  showing  the  lock- 
ing arrangement  of  any  particular  interlocking  hiachine.  The 
dog  chart  for  the  Saxby  and  Farmer  machine  is  made  up  with  the 


MECHANICAL  INTERLOCKING 


45 


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RAILWAY  SIGNALING 


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MECHANICAL  INTERLOCKING 


47 


front  of  the  locking  bed  at  the  top  just  as  an  observer  would  see 
it  if  he  were  standing  at  the  back  of  the  machine  and  facing  the 
operator  in  position  to  manipulate  the  levers.  This  throws 
lever  1  to  the  right-hand  side  on  the  drawing,  as  shown  in  Fig.  41. 
The  figures  across  the  top  represent  numbers  of  the  levers,  while 
those  on  the  side  refer  to  the  locking  bars.  The  circles  represent 
the  points  where  the  locking  shafts  connect  to  the  locking  bars. 
On  the  dog  chart  for  the  Style  A  machine,  illustrated  in  the 
same  figure,  the  back  locking  is  shown  above  the  front  locking. 


FIG.    44. — The    Johnson    interlocking 
machine. 


FIG.  43.—  The  National  interlock- 
ing machine. 

D 

1  are  back  and  front  locking  spaces  of  the  first  or  top  plate; 


2  are  back  and  front  locking  spaces  of  the  second  locking 


D 


plate;  and  so  on  to  „     4.     The  position  of  lever  1  is  at  the  left 

on  the  sheet. 

Figure  42  shows  dog  charts  for  Saxby  and  Farmer  and  Style  A 
machines  to  operate  a  trailing  point  crossover  between  double- 
track  lines. 

Figure  43  represents  a  National  interlocking  machine  while 
Fig.  44  represents  a  Johnson. 


48 


RAILWAY  SIGNALING 


The  vertical  locking  plant  requires  less  room  than  the  hori- 
zontal, but  has  more  wear  between  the  dogs  and  the  notches  in  the 
tappets.  In  the  case  of  the  vertical  locking  plant  the  locking  is 
below  the  floor,  while  in  the  case  of  the  horizontal  locking,  it  is 
above  the  floor.  Lying  below  the  floor,  often  in  a  dark  room,  the 
vertical  locking  frequently  does  not  get  the  attention  and  care  it 
should  have.  ,-> 


FIG.  45. — The  Stevens  interlocking  machine. 

27.  Stevens  Interlocking  Machine. — A  dwarf  type  of  inter- 
locking machine  constructed  with  lever  instead  of  latch  locking  is 
known  as  the  Stevens.  It  operates  with  a  vertical  type  of  locking 
placed  in  a  horizontal  bed,  but  the  stroke  of  the  tappet  is  much 
longer  than  is  the  case  with  the  Style  A  machine.  It  is  used 
principally  where  a  number  of  yard  switches  can  be  controlled 
from  a  central  point  or  where  it  is  desired  to  install  some  form  of 
temporary  interlocking. 


CHAPTER  V 

MECHANICAL  INTERLOCKING 
OTHER  EQUIPMENT 

28.  Leadouts. — The  equipment  that  transfers  the  motion  from 
the  levers  in  the  tower  to  the  horizontal  pipes  and  wires  on  the 
ground  is  called  the  leadout.  It  includes  all  of  the  vertical  pipes 
and  wires  within  the  tower  and  all  the  rocking  shafts,  cranks,  and 


FIG.  46. — Rocking  shafts  for  leadouts. 

deflecting  bars  in  the  case  of  pipes,  and  wheels  and  chains  in  the 
case  of  wires  that  connect  the  pipes  and  wires  inside  with  those 
outside  the  building.  In  the  case  of  the  rocking  shaft,  shown  in 
Fig.  46,  the  vertical  pipe  connects 
with  the  outside  arm  and  the  hori- 
zontal pipe  with  the  adjustable 
inside  arm.  The  shaft  itself  may  be 
either  square  or  hexagonal,  as  the 
figure  illustrates,  the  square  ones 
being  most  commonly  found  in 
practice. 

Figure  47  represents  a  vertical  crank  and  Fig.  48  a  horizontal 
and  a  vertical  deflecting  bar.     The  horizontal  crank  is  illustrated 
4  49 


FIG.  47. — R.  S.  A.  vertical  crank. 


50 


RAILWAY  SIGNALING 


in  Fig.  60.  In  the  case  of  the  deflecting  bar,  the  curved  bar 
slides  between  two  sets  of  rollers  supported  by  the  frame.  Figure 
49  shows  the  use  of  both  rocking  shafts  and  deflecting  bars  in  a 
leadout. 

29.  Pipes  and  Couplings. — The 
movements  of  the  levers  in  a 
mechanical  plant  are  transmitted 
to  the  derails,  home  signals,  and 
switches  by  means  of  1-in.  iron 
pipes,  and  to  distant  signals  by 
means  of  No.  8  or  9  steel  wire. 
Home  signals  and  dwarf  signals 
are  sometimes  operated  by  wires. 
The  ends  of  the  pipes  are  fastened 
together  by  means  of  couplings 
over  the  outside  and  3^2~in-  steel 
plugs  10  in.  long  on  the  inside,  as 
illustrated  in  Fig.  50.  Two  Ji-in. 
rivets  pass  through  each  plug  at 
the  end  of  each  pipe.  The  pipe 
is  fastened  to  a  crank  by  means  of 
a  steel  rod  with  a  tang  on  one  end 
vertical  and  a  solid  or  screw  jaw  on  the 
other,  a  number  of  different  forms 
of  which  are  shown  in  Fig.  51. 

30.  Stuffing  Box. — It  very  often  becomes  necessary  to  carry 
pipe  lines  under  a  street,  in  which  case  the  pipes  are  placed  inside 
of  larger  pipes  enclosed  at  the  ends  by  stuffing  boxes,  as  illustrated 
in  Fig.  52.     The  outer  pipes  are  filled  with  oil  to  preserve  the 
materials  and  to  eliminate  the  friction. 

31.  Pipe  Carriers. — Pipes  are  supported  on  pipe  carriers  placed, 
as  a  rule,  7  ft.  apart  on  straight  lines  and  6  ft.  apart  on  curves. 
This  length  of  space  prevents  buckling  when  the  pipe  is  in  com- 
pression.    The  distance  center  to  center  of  levers  in  a  mechanical 
plant  is  5  in.,  while  the  distance  center  to  center  of  pipes  as  they 
are  placed  in  the  carriers  is  2%  in.     The  two  rollers  in  the  carrier, 
the  one  below  and  the  other  above  the  pipe,  tend  to  reduce  the 
amount  of  friction  during  the  movement  of  the  pipe  line.     Where 
there  is  only  one  set  of  rollers  in  the  frame  it  is  called  a  one-way 
carrier;  where  there  are  two,   a  two-way  carrier;  and  so  on. 
The  pipe  carrier  is  fastened  to  its  foundation  by  means  of  a  pipe 


FIG. 


48. — Horizontal    and 
deflecting  bars. 


MECHANICAL  INTERLOCKING 


51 


carrier  base.  The  transverse  carriers,  represented  by  Fig.  54, 
rest  on  two  track  ties  and  carry  the  pipes  under  the  rails  at 
right  angles  to  the  track. 


TOWER   LEADOUTS 

(MOUNTED  DEFLECTING  BARS  AND  ROCKING  SHAFTS) 


RSA 
1206 


FIG.  49.— R.  S.  A.  tower  leadout. 


32.  Compensators.— Compensators  are  inserted  at  the  proper 
places  in  pipe  and  wire  lines  to  provide  automatically  for  changes 
in  length,  due  to  expansion  or  contraction  caused  by  differences 


52 


RAILWAY  SIGNALING 


C^ffi^M^ 


So  ft  Iron  RIVET  - 


COUPLING 

FIG.  50. — R.  S.  A.  1-in.  pipe  and  coupling. 


FIG.  51. — Solid  and  screw  jaws. 


FIG.  52.— R.  S.  A.  standard  stuffing  box. 


MECHANICAL  INTERLOCKING 


53 


in  temperature.     In  the  case  of  a  pipe  line,   the  compensator 
reverses  the  direction  of  motion  so  that  the  change  in  length  on 


FIG.  53. — Pipe  carrier.     Universal  base. 

one  side  of  it  will  just  offset  the  change  on  the  other  side.  Where  a 
line  is  straight  and  one  compensator  is  used,  it  should  be  in  the 
middle.  If  two  are  used,  they  should  be 
located  at  the  quarter  points.  The  com- 
pensator used  in  straight  pipe  line  con- 
struction is  called  a  "lazy  jack."  It  is 
made  of  two  angles,  60  and  120  degrees, 
with  a  link  connecting  them,  as  shown  in  Fig.  55. 


FIG.  54.— R.  S.  A. 
two-way  transverse 
pipe  carrier. 


One 


FIG.  55. — R.  S.  A.  "lazy  jack"  pipe  compensator. 

compensator  is  used  for  a  pipe  50  to  650  ft.  long  and  two  for  a 
line  between  650  and  1,300  ft.     In  the  case  of  a  90-degree  change 


54  RAILWAY  SIGNALING 

in  the  direction  of  a  line,  a  crank  if  properly  placed  may  be  used 
as  a  compensator.  Figure  56  illustrates  a  straight  arm  com- 
pensator. 

The  following  example  will  serve  to  illustrate 
the  principle  of  applying  compensation  to  a  pipe 
line:  A  pipe  as  a  part  of  an  interlocking  plant  is 
used  to  throw  switches  1  and  2  of  a  main-line 
crossover.     The  switches  are  normally  lined  up 
FIG.  56.— R.  s.  for  the  main  tracks  clear.     The  dimensions  of  the 
A.  straight  arm  track  layout  are  given  in  the  sketch,  Fig.  57. 

compensator.  ,111,.  i         ,  -   , 

The  motion  from  the  leadout  is  a  push,  which 
causes  a  pull  beyond  the  first  compensator.  Since  the  motion  to 
be  given  to  the  switch  1  is  a  push,  the  angle  crank  at  A  should  be 
a  compensator.  The  direction  of  motion  beyond  the  second  com- 
pensator is  a  push;  and  since  the  motion  to  be  given  switch 
2  is  a  pull,  the  crank  at  B  should  also  be  a  compensator. 
The  calculated  locations  of  the  "lazy  jacks"  are  shown  in  the 
figure. 

Should  a  compensator  figure  to  come  where  a  pipe  carrier  is 
located,  the  compensator  should  be  placed  at  the  middle  of  the 
adjoining  span. 


m 

->        ^      +-              *=    V*-^ 

3 

""7"                                             K—  -y«S5f-'    ----*.-  ---109.5;  

g 

FIG.  57. — Compensation. 

The  following  table,  Fig.  58,  shows  the  lengths  and  positions 
of  crank  arms  recommended  by  the  Railway  Signal  Association 
for  compensation. 

A  type  of  wire  compensator  is  shown  in  Fig.  59.  It  operates 
by  means  of  the  lever  at  the  base  of  the  post  and  is  so  arranged 
that  the  tension  on  the  two  wires  will  be  constant.  On  one  arm 
of  the  lever  are  two  chain  wheels  and  on  the  other  is  a  rather 
heavy  counterweight .  When  the  wires  shorten ,  the  counterweight 
rises;  when  they  lengthen,  the  counterweight  drops,  adjusting 
the  length  automatically. 


MECHANICAL  INTERLOCKING 


55 


33.  Field  construction  of  pipe  lines  as  recommended  by  Com- 
mittee II  of  the  Railway  Signal  Association  in  Volume  XIV, 
1917,  of  the  Proceedings:1 


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MOTE:  Since  the  mean  temp,  vanes,  I'f  must  be  taken 
for  thelcxtifude  where  the  work  is  done. 

FIG.  58. — R.  S.  A.  compensation  table. 

1.  When  laying  out  a  pipe  line,  the  selection  of  a  place  as  free  as 
possible  from  fixed  obstructions,  such  as  buildings,  bridge  girders,  abut- 
ments, etc.,  should  be  given  first  consideration.  The  alignment  of  the 
pipe  line  should  be  straight  when  practicable.  Often  by  slightly  chang- 
ing the  distance  the  pipe  line  is  located  from  the  rail,  some  fixed  obstruc- 
tion can  be  avoided  and  the  line  kept  straight.  Where  the  pipe  line 

1  Page  395. 


56 


RAILWAY  SIGNALING 


follows  a  turnout,  the  curve  in  the  pipe  line  should  be  gradual  instead  of 
following  the  rather  sharp  curve  of  the  turnout,  and  the  maximum 
curvature  should  not  exceed  (10)  degrees. 

2.  Where  the  interlocking  station  building  is  set  back  far  enough  from 
the  tracks  so  that  an  additional  track  may  be  laid  in  front  of  the  building 
at  some  future  time,  the  pipe  line  should  be  installed  the  standard  dis- 
tance from  the  proposed  track,  unless  extraordinary  expense  would  be 

incurred,  rather  than  install  the 
line  near  the  present  track  and 
later  move  it  when  the  proposed 
track  is  laid. 

3.  In  case  the  pipe  line  is  to  be 
run  on  a  bank,  sufficient  space 
should   be  provided  to  strongly 
brace  the  foundations.     In  case 
the  line  is  to  be  run  in  a  ditch, 
proper  drainage  should  be  pro- 
vided; also  the  slopes  of  banks 
should  be  graded  or  a  wall  con- 
structed to  prevent  earth  sliding. 
Pipe    lines   should   not    be  run 
under  station  platforms  where  it 
can  be  avoided. 

4.  Where  necessary  to  run  pipe 
lines  under  ground,  as  at  road 
crossings,  platforms,  water  tubs, 
stand   pipes,   etc.,  it   is   recom- 
mended that  where  proper  drain- 
age   can    be    provided    concrete 
side  walls  with  plank  covering 
be  used  around  the  pipe  line;  at 


FIG.  59. — Wire  compensator. 


points    where    proper    drainage 
cannot    be   provided   each    pipe 

should   be  run  in  a  larger  pipe  with  oil  and  provided  with  a  stuffing 

box  on  each  end. 

5.  Stakes  showing  the  final  elevation  of  the  rail  should  be  accurately 
driven  every  fifty  feet,  then  by  using  intermediate  stakes  a  line  should 
be  stretched  from  which  the  foundations  should  be  set. 

6.  The  location  of  crank  and  bolt-lock  foundations  should  be  determined 
upon  first  in  order  that  pipe  carrier  foundations  can  be  so  spaced  as  not 
to  interefere  with  cranks  and  bolt-locks.     Piles  should  be  driven  for 
supporting  crank,  compensator  and  bolt-lock  foundations   (and  pipe 
carrier  foundations  if  necessary)  where  the  ground  is  swampy  or  marshy. 
Everything  should  be  done  to  have  the  support  for  all  pipe  line  apparatus 
as  solid  as  possible  and  sufficiently  braced  to  prevent  shifting. 


MECHANICAL  INTERLOCKING 


57 


7.  In  providing  compensation  for  pipe  lines  the  mean  temperature  of 
the  interlocking  location  should  be  known;  in  most  cases,  it  will  be  the 
same  as  at  the  nearest  city  and  can  be  obtained  from  the  Weather 
Bureau.     R.  S.  A.  Drawing  1102,  Compensation  Table,  must  be  used 
when  cutting  in  pipe  lines. 

8.  Crosspipes  should  not  be  installed  until  all  ties  supporting  pipe 
carriers  are  properly  spaced  and  tamped  and  all  tracks  are  brought  to 
the  final  elevation  and  line,  which  should  be  the  same  for  all  tracks  in 
the  interlocking  limits. 

9.  Crank  and  compensator  foundations  should  be  set  to  template  so 
that  with  the  crank  and  compensator  arms  both  normal  and  reversed 
the  center  of  the  hole  in  the  arm  will  coincide  with  the  center  of  the  pipe 
line.     Rough  forms  should  be  used  for  the  bottoms  of  foundations 
where  necessary;  but  finished  knock-down  forms  should  be  used  for  the 
top  portions  of  the  foundations.     Where  foundations  are  likely  to  be 
disturbed  by  frost,  cinders  should  be  placed  in  the  bottom  of  the  founda- 
tion hole  as  well  as  around  the  sides,  the  rough  forms  being  made  of 
uniform  slope  and  left  in  the  ground. 

10.  Concrete  for  foundations  should  be  mixed  at  a  central  point  where 
practicable,  from  which  it  can  be  distributed  to  foundation  locations  by 
track  barrows  or  dollies,  or  mixed  on  a  flat  car  which  can  be  pushed  from 
one  point  to  another. 

34.  Horizontal  Cranks  and  Radial  Arms. — An  abrupt  change 
in  the  horizontal  direction  of  a  pipe  line  may  be  made  by  means 


HOLE 


FIG.  60. — R.  S.  A.  one-,  two-,  and  three-way  cranks. 

of  an  angle  crank,  deflecting  bar,  or  radial  arm.  The  most  com- 
monly used  of  these  is  the  angle  crank,  which  may  be  one-way, 
two-way,  or  three-way,  as  shown  in  Fig.  60.  The  angle  between 
the  arms  is  usually  90  degrees,  although  other  angles  both  smaller 
and  larger  are  occasionally  used.  Figure  61  represents  an  acute 
angle  crank.  A  three-arm  crank,  illustrated  in  Fig.  62,  is  used 
extensively  in  connection  with  switch  arrangements.  The  radial 
arm,  shown  in  Fig.  63,  is  convenient  for  changing  directions 


58 


RAILWAY  SIGNALING 


where  the  angle  is  comparatively  small.     A  horizontal  deflecting 
bar  is  shown  in  Fig.  48.     Where  the  change  in  direction  is  gradual, 


FIG.  61.— R. 
S.  A.  acute  angle 
crank. 


FIG.  62.  — R. 
S.  A.  three-arm 
crank. 


FIG.    63.— R.   S. 
A.  radial  arm. 


as  when  following  an  easy  curve  in  the  track,  the  pipes  may  be 
sprung  into  place. 


0 


FIG.  64o. — Foundations  for  cranks,  wheels,  and  compensators. 

35.  Crank,  Wheel,  Compensator,  and  Pipe  Carrier  Founda- 
tions.— Figure  64a  represents  designs  of  concrete  foundations 


/HOLE 


FIG.  646. — R.  S.  A.  pipe  carrier  foundation. 

for  cranks,  wheels,  and  compensators.     Figure  646  illustrates 
a  design  of  a  foundation  for  a  pipe  carrier.     The  foundations 


MECHANICAL  INTERLOCKING 


59 


should  be  large  enough  to  eliminate  any  possibility  of  their 
shifting  due  to  the  movement  of  the  pipes. 

36.  Facing  Point  Lock. — To  insure  that  a  switch  or  point  derail 
is  properly  closed  and  held  in  that  position,  some  kind  of  locking 
equipment  becomes  necessary.  Two  devices  have  been  used 
for  the  purpose,  facing  point  locks,  and  switch  and  lock  move- 
ments. In  the  case  of  facing  point  locks,  two  levers  are  neces- 
sary, one  to  throw  the  switch  or  derail  and  the  other  to  lock  it. 
Switches  are  locked  in  both  open  and  closed  positions.  To 
throw  the  switch,  the  plunger  is  pulled  back  far  enough  to  clear 
the  lock  rod,  one  end  of  which  is  fastened  to  the  point  of  the 
switch  and  the  other  is  flattened  and  passes  through  the  facing 


FIG.  65. — Facing  point  lock. 

point  lock  casting.  After  the  switch  is  thrown  and  is  in  the 
proper  position,  the  plunger  is  pushed  back  through  a  second 
hole  in  the  lock  rod,  holding  the  switch  points  firmly  and  prevent- 
ing them  from  springing  open  while  a  train  is  passing  over.  The 
plunger  of  a  facing  point  lock  should  not  be  placed  between  the 
rails,  nor  at  any  point  where  a  dragging  brakebeam  can  strike  it 
and  bend  it  over  or  tear  it  out.  Figure  65  illustrates  a  facing 
point  lock. 

37.  Switch  and  Lock  Movement. — The  switch  and  lock 
movement,  a  mechanism  so  constructed  as  to  throw  the  switch 
and  lock  it  all  with  one  lever  movement,  is  shown  in  Fig.  66.  In 
the  figure  the  pipe  from  the  lever  is  connected  to  the  slide  bar 
14-15.  Another  bar  runs  from  escapement  crank  20  to  the  switch 
or  derail  point.  Between  upper  slide  bar  12  and  lower  slide 
bar  13  is  a  roller,  21.  As  the  slide  bar  is  pushed  or  pulled,  the 


60 


RAILWAY  SIGNALING 


roller  engages  the  escapement  crank,  causing  arm  20  to  move, 
shifting  the  switch  or  derail.  There  is  a  short  plunger  that 
passes  through  a  hole  in  the  lock  rod  as  in  the  case  of  the  facing 
point  lock.  The  first  part  of  the  throw  of  the  lever  unlocks  the 
switch  or  derail  and  throws  the  detector  bar  described  in  the 
following  paragraph;  the  second  part  throws  the  switch  or  derail; 
and  the  third  part  locks  it  in  its  new  position. 


//•  ?'        a    21 

FIG.  66. — Switch  and  lock  movement. 

38.  Detector  Bar. — A  detector  bar  is  a  device  so  constructed 
and  operated  as  to  prevent  towermen  from  throwing  a  switch  or 
derail  under  a  moving  train.     It  is  a  flat  bar  of  steel  %  to  J-^  in. 
thick,  2J4  in.  high,  and  53  ft.  long,  placed  along  the  side  of  the 
rail  and  held  in  position  by  clips.     The  bar  is  connected  to  the 
same  pipe  that  throws  the  plunger  of  the  facing  point  lock  or 
that  operates  the  switch  and  lock  movement.     As  these  functions 
are  thrown,  the  detector  bar  must  travel  horizontally  parallel 
to  the  rail.     It  is  so  constructed  that  while  it  moves  horizontally 
it  must  also  move  vertically,  rising  as  it  moves  an  inch  or  more 
above  the  top  of  the  rail.     If  a  train  should  be  standing  or  moving 
on  the  rail,  any  attempt  to  throw  the  switch  or  derail  would 
fail  when  the  detector  bar  rises  against  the  tread  of  the  wheel. 
Four  different  types  of  detector  bars  are  shown  in  Fig.  67. 

39.  Bolt  Lock. — The  bolt  lock  is  an  appliance  to  guarantee  that 
the  home  signal  cannot  be  placed  in  the  proceed  position  until 
the  derail  or  switch  is  cleared.     In  addition  to  the  throw  rod  and 
lock  rod,  another  rod  or  bar  is  sometimes  connected  to  the 
switch  point  or  derail.     This  bar  extends  out  to  cross  the  pipe 


MECHANICAL  INTERLOCKING 


61 


or  wire  line  that  operates  the  home  signal.  In  the  pipe  line  at 
this  particular  point  is  inserted  a  flat  bar.  Each  of  these  bars 
crossing  at  right  angles  has  a  notch  so  placed  as  to  preclude  a 
certain  order  of  switch  and  signal  movement.  If  for  any  reason 


s 
1 

o 

t 
IS 

I 


the  switch  should  fail  to  be  moved,  even  though  its  signal  lever 
had  been  thrown,  the  home  signal  could  not  be  operated.  Figure 
68  shows  a  one-way  bolt  lock.  All  of  these  additional  precautions 
and  safety  devices  are  installed  to  guarantee  against  any  possi- 
bility of  failure  on  the  part  of  pipes  or  other  ground  equipment. 


62 


RAILWAY  SIGNALING 


40.  Head  Rod  and  Switch  Adjustment. — The  two  switch 
points  are  connected  near  the  end  by  a  head  rod  shown  in  Fig.  72. 
If  track  circuits  are  installed  for  any  purpose,  it  becomes  neces- 


fHOU 


FIG.  68. — One-way  bolt  lock. 

sary  to  insulate  the  two  rails  to  avoid  a  short-circuit.  To  ac- 
complish this,  some  kind  of  fiber  is  generally  used  for  insulation. 
To  this  head  rod  is  fastened  one  end  of  the  throw  rod  that 


y  y  y  y 


FIG.  69.— R.  S.  A.  insulated  rods. 


operates  the  switch.  There  is  an  adjusting  arrangement  where 
the  throw  rod  connects  to  the  head  rod  whereby  the  former 
moves  a  certain  distance  before  it  begins  to  throw  the  switch. 


FIG.  70. — Switch  adjustment. 

This  is  done  to  offset  a  part  of  the  difference  in  travel  between 
the  lever  throw  and  the  switch  movement.  The  remainder  of 
the  difference  is  taken  up  by  using  unequal  lengths  of  crank 
arms. 


MECHANICAL  INTERLOCKING 


63 


41.  Lock  Rod. — An  insulated  front  rod  and  a  lock  rod  used  in 
connection  with  facing  point  locks  and  switch  and  lock  move- 
ments is  shown  in  Fig.  71.  Figure  72  represents  a  switch  locked 


ENLARGED  VIEW  OF  INSULATION 


FIG.  71. — Insulated  front  and  lock  rods. 

by  a  facing  point  lock  after  it  is  thrown  by  a  separate  lever,  and 
Fig.  73  represents  a  switch  operated  by  a  switch  and  lock  move- 
ment. In  both  cases  the  detector  bar  and  bolt  lock  attachment 


FIG.  72. — Facing  point  lock  and  bolt  lock  applied  to  a  switch. 

are  added.  The  detector  bar  stands  in  front  of  the  switch  points. 
Figure  74  shows  the  layout  for  a  double  slip  switch  with  movable 
point  frogs.  One  lever  operates  by  means  of  a  three-way  crank 


FIG.  73. — Switch  and  lock  movement  and  bolt  lock  applied  to  a  switch. 

and  a  rocker  shaft  one  facing  point  lock  for  each  pair  of  slip 
switches. 


64 


RAILWAY  SIGNALING 


MECHANICAL  INTERLOCKING 


65 


42.  Derails. — There  are  three  types  of  derails  used  in  connec- 
tion with  interlocking  plants.  The  oldest  is  the  split  point,  shown 
in  Fig.  75.  As  this  has  one  rail  broken  it  has  the  disadvant- 
age of  making  the  track  somewhat  unsafe,  and  therefore  is  used 
most  frequently  in  low-speed  routes.  The  Hayes,  one  of  the 


n 


FIG.  75.— Split  point  derail. 


lifting  block  type,  shown  in  Fig.  76,  rests  on  top  of  the  rail  when 
set  to  stop  traffic;  and  although  it  allows  the  rails  to  be  continu- 
ous, it  is  used  largely  on  medium-speed  and  low-speed  routes. 
The  lifting  rail  type,  one  form  of  which  is  shown  in  Fig.  77,  is  so 
built  that  a  sharp  point  fits  against  the  inside  of  one  rail  and'a  flat 


FIG.  76.— Hayes  derail. 

riser  point  against  the  outside  of  the  head  of  the  outer  rail  when 
set  to  stop  traffic.  The  sharp  point  derails  the  wheels  on  one  side 
while  the  flat  point  lifts  those  on  the  other  side  high  enough  to 
allow  the  flange  to  clear  the  top  of  the  rail.  In  this  type  both 

5 


66 


RAILWAY  SIGNALING 


track  rails  are  continuous.  Several  others  are  built  on  the  same 
principle,  some  of  which  have  the  flat  point  lying  on  top  of  the 
rail  instead  of  on  the  side  of  it.  The  two  points  are  connected  by 
means  of  tie  rods  and  are  moved  simultaneously  into  positions 


FIG.  77. — Morden  derail. 


for  clearing  or  derailing  trains.     This  type  is  used  principally  on 
high-speed  routes. 

43.  Crossing  Bars. — Crossing  bars  are  used  at  interlocking 
plants  to  prevent  a  towerman  from  changing  a  line-up  while  a 


FIG.  78. — Crossing  bars. 

car  or  locomotive  is  standing  on  a  railroad  crossing.  They  are 
just  ordinary  detector  bars  placed  as  near  to  the  crossing  frog  as 
possible,  one  on  each  side  of  the  crossing  in  each  track.  These 
bars  lock  the  derails  both  normal  and  reversed  so  that  they  cannot 


MECHANICAL  INTERLOCKING 


67 


be  moved  without  operating  the  crossing  bars.  If  a  car  should  be 
standing  on  the  crossing,  it  would  be  impossible  to  move  the  bar 
and  hence  impossible  to  change  the  derails  and  the  signals  on  that 
route. 

44.  Semaphore  Signals. — Figure  79  shows  the  method  of  con- 
structing and  operating  a  one-arm  two-position  lower  quadrant 
signal.  The  left-hand  signal  is  operated  by  a  pipe  line  with  the 


FIG.  79. — One-arm  two-position  lower  quadrant  signals. 


counterweighted  lever  near  the  base  of  the  post,  while  the  right- 
hand  signal  is  controlled  by  a  wire  line  and  chain  running  through 
a  wheel  at  the  base  of  the  post  and  the  counterweighted  lever 
more  than  half  way  up  on  the  post.  Two  wires  are  required  to 
operate  the  signal.  The  post  is  made  of  three  lengths  of  pipe,  4, 
5,  and  6  in.  in  diameter. 

Figure  80  illustrates  a  pipe  and  wire  operated  two-arm  two- 
position  signal.  The  details  of  upper  quadrant  one  and  two-arm 
signal  construction,  as  recommended  by  the  Railway  Signal 


68 


RAILWAY  SIGNALING 


Association,  are  shown  in  Fig.  81,  a  and  b.  The  mast  proper 
of  the  one-arm  signal  is  25  ft.  high,  made  up  of  two  lengths  of 
5-  and  6-in.  pipe  swaged  together  at  the  joints.  The  pinnacle,  3, 
brings  the  total  height  up  to  26  ft.  8  in.  above  the  foundation. 
The  spectacle  casting,  8,  has  three  roundels,  or  glasses,  properly 
spaced  to  allow  for  the  45-  and  90-degree  positions  of  the  signal. 
The  lamp  is  attached  to  the  post  just  behind  the  right-hand 


FIG.  80. — Two-arm  two-position  lower  quadrant  signals. 

roundel.  The  blade,  9,  is  made  either  of  wood  or  sheet  metal. 
The  up-and-down  rod,  11,  is  a  1-in.  pipe  fitted  to  the  casting  of 
the  arm  and  the  angle  crank  at  the  base  to  operate  the  signal. 
The  upper  quadrant  type  of  construction  does  not  need  the  coun- 
terweighted  arm.  All  the  appliances  are  attached  to  the  post 
by  means  of  clamps.  The  foundation  and  anchoring  plans  are 
also  shown  in  the  figure. 


MECHANICAL  INTERLOCKING 


69 


Figure  81c  represents  a  three-arm  signal  that  corresponds  to 
the  arrangement  in  Scheme  3,  Appendix  B.  A  two-position 
bracket  signal  is  shown  in  Fig.  82,  while  some  of  the  details  of 
construction  of  a  three-arm  bridge  or  bracket  signal  are  presented 
in  Fig.  83.  Figure  84  is  a  cantilever  attachment  for  a  doll  post. 


FIG.  81. — R.  S.  A.  standard  upper  quadrant  signals. 


45.  Dwarf   Signals. — Figure   85   represents  a  one-arm   two- 
position  upper  quadrant  dwarf  signal.     Attached  to  the  operating 
mechanism  is  a  spring  that  is  placed  under  compression  when  the 
proceed  indication  of  the  signal  is  given  so  that  if  the  wire  line 
that  operates  the  signal  fails  the  blade  automatically  goes  to 
the  stop  position.     The  blade  of   the  dwarf  signal  is  made  flex- 
ible so  that  it  can  be  struck  without  injury.    Figure  86  is  a 
Railway  Signal  Association  upper  quadrant  pipe-operated  dwarf 
signal. 

46.  Time  Lock. — A  time  lock  illustrated  in  Fig.  88  is  a  mechan- 
ical appliance  used  in  connection  with  the  home  signal  lever  of  a 
mechanical  interlocking  plant  to  prevent  the  towerman  from 


70 


RAILWAY  SIGNALING 


FIG.  82. — Two-position  lower  quadrant         FIG.  83. — R.  S.  A.  three-arm  upper  quad- 
bracket  signal.  rant  bracket  or  bridge  signal. 


FIG.  84. — Cantilever  bracket. 


MECHANICAL  INTERLOCKING 


71 


quickly  changing  a  line-up  after  it  has  been  accepted  by  a  train. 
A  heavy  rack,  supported  vertically,  is  raised  quickly  by  reversing 
the  lever,  and  is  held  in  that  position  until  the  lever  is  thrown 
towards  the  normal  position.  As  soon  as  the  lever  is  placed 


FIG.  85. — One-arm  two-position  upper  quadrant  dwarf  signal. 

normal,  however,  the  support  for  the  rack  is  removed,  and  the 
rack  is  dropped  very  slowly.  There  is  nothing  to  prevent  the 
towerman  from  returning  the  home  signal  lever  to  normal,  but 
he  cannot  release  his  latch  until  the  rack  runs  down. 


u 


FIG.  86. — R.  S.  A.  dwarf  signal  for  pipe  connection. 


The  weight  of  the  rack  actuates  a  double  pendulum  in  such  a 
manner  that  each  swing  of  the  pendulum  drops  the  rack  one 
tooth.  A  roller  on  the  end  of  the  cross-lock  connected  with  the 
locking  bed  in  the  case  of  the  Saxby  and  Farmer  machine,  en- 


72 


RAILWAY  SIGNALING 


gages  the  back  of  the  rack  and  prevents  the  lever  latch  from 
being  placed  entirely  normal  while  the  rack  is  up.  There  is  a 
notch  in  the  back  of  this  rack  located  at  just  the  point  to  contain 


N0.20-STAMPED  Bit.- 

TKWS 


I  BODY  OF  LAMP  SHALL  BE  MADE  OF 
NO.  8  SHEET  STEEL  TINNED. 

2.  RIVETS  SHALL  BE  USED  IN  CONSTRU- 
CTION OF  THE  BODY  OF  THE  LAMP 
FOR  HOLDING  PARTS  TOGETHER. 

3.  HANDLE  OF  LAMP  SHALL  BE  NO.  4 
B.W.G.  STEEL  WIRE.  I 

4.  DOOR  SHALL  HAVE  WATER-SHED  SO 
ARRANGED  AS  TO  PREVENT  RAIN 
ENTERING  THE  LAMP,  DOOR  SHALL 
RAISE  HIGH  ENOUGH  TO  MAKE  THE 
OPENING  SIX  AND  FIVE -EIGHTHS 

5.  LAM>  SHALL  H«VE  TOP  DRAUGHT    "001 
VENTILATION.  (VENTILATION  WILL       l'_ / 

BE  TESTED  WHEN  REQUIRED  AT  THE  BTRivETS 

FACTORY  AS  FOLLOWS:  'A'  WIND 

VELOCITY  EQUIVALENT  TO  EIGHTY 

(80)  M.P.H.  FOR  TWO  (2)  MINUTES. 

•§•  STILL  AIR  TEMPERATURE  ONE 

HUNDRED  AND  TEN  (110)  DEGREES  FAHR. 

FOR  TWO  (2)  HOURS).  THE  LAMP 

WILL  BE  REJECTED  IF  EITHER  OF 

THE  ABOVE  TESTS  EXTINGUISH 

THE  FLAME. 

6.  LENS  SHALL  BE  (SEE  REFERENCE  N(&)  INCHES  IN 
DIAMETER  WITH  THREE  AND  ONE- 
HALF  (3i)  INCH  FOCUS. 

7.  LENS  HOLDER  SHALL  BE  ARRANGED 
SO  THAT  LENS  CAN  BE  EASILY  RE- 
MOVED AND  SHALL  COMPLETELY 
ENCIRCLE  THE  LENS . 

i  SOCKET  NOT  TO  EXCEED  THE  DI- 
MENSIONS OF  BRACKET  MORE  THAN 
ONE-SIXTEENTH  (ft)  INCH  AND  BE 
EIGHT  (8)  INCHES  IN  DEPTH,  RE- 
CESSED TO  FIT  STANDARD  LAMP 
BRACKET.  (R.S.  A.  1049) 

9.  BACK  LIGHT  AND  PEEP-HOLE  GLASSES 
SHALL  BE  HELD  IN  PLACE  BY     .  I 

(11006)     SCREW  RETSMNIN6    ~^ 
RINGS. 

10.  INSECT  SCREEN  SHALL  BE  PRO- 
VIDED WHEN  SPECIFIED. 


11007  MALLEABLE  POCKET 

TO  RECEIVE  POINTED  LUG  OF 
LAMP  BRACKET  R.S. A.  1049 


SCALE  OF  INCHES 


-fv,(DIAMrrER} 
IIOOIS   LAMP  COMPL.WITH  5"  LENS 


SEMAPHORE  LAMP 

(OETAIL   AND  ASSEMBLY) 


FIG.  87. — R.  S.  A.  semaphore  lamp. 

the  roller  when  the  rack  is  entirely  down.  The  cross-lock  is  free 
to  move  when  the  rack  is  down,  releasing  the  home  lever  latch 
and  allowing  it  to  finish  its  throw  to  normal.  After  the  latch  is 


MECHANICAL  INTERLOCKING 


73 


in  its  normal  position,  the  derail  may  be  opened  and  another 
route  lined  up.  In  the  case  of  the  Style  A  machine  the  cross- 
lock  is  connected  with  one  end  of  the  rocker-link,  but  its  action  is 
practically  the  same. 

These  time  locks  are  so  adjusted  as  to  require  from  one  minute 
to  one  minute  and  twenty  seconds  or  even  longer  to  run  down. 
This  means  that  the  tower- 
man  will  have  to  wait  this 
amount  of  time  to  throw  the 
derail  after  he  has  thrown 
the  home  signal  to  danger. 
The  length  of  that  time  would 
be  sufficient  to  allow  a  train 
running  at  average  high-speed 
at  the  distant  signal  to  get 
far  enough  over  the  plant  to 
be  out  of  danger  or  to  come 
to  a  stop  before  the  tower- 
man  would  have  time  to  open 
the  derails,  should  he  sud- 
denly decide  to  take  the 
signals  away  from  this  train 
and  give  them  to  another  on 
a  conflicting  route. 

47.  Calling-on  Arm.  — It 
sometimes  becomes  neces- 
sary when  a  home  signal  is 
used  for  interlocking  where 
block  signal  circuits  are  in 
operation,  to  install  what  is  termed  a  calling-on  arm  signal. 
After  a  train  has  passed  the  home  signal  in  such  an  installation, 
the  signal  automatically  goes  to  the  stop  position.  There  are 
times  while  this  train  is  making  'the  station  or  other  stop  and 
thereby  preventing  the  home  signal  from  being  cleared,  that  it 
becomes  expedient  to  signal  a  following  train  to  pass  the  home 
signal  and  proceed  slowly  towards  the  station  or  other  point  in 
the  interlocked  territory.  To  advance  the  second  train  past  the 
home  signal  the  towerman  must  use  the  calling-on  arm.  It  is 
mounted  on  the  same  post  as  the  home  signal  arm,  but  generally 
has  a  shorter  blade.  It  is  operated  independently  of  any  track 
circuit  by  the  same  kind  of  mechanical  or  power  appliances  as  are 


FIG.  88.— Time  lock. 


74 


RAILWAY  SIGNALING 


used  to  throw  the  derails  and  switches.  In  c,  Fig.  81,  the  upper 
blade  governs  the  superior  route,  the  middle  one  the  inferior 
route,  and  the  lower  one  may  be  a  calling-on  arm  for  either. 

48.  Movable  Bridge  Couplers  and  Locks. — Figure  89  shows  the 
four-way  bridge  coupler  used  to  open  and  close  pipe  lines  where 


FIG.  89. — Swing  bridge  coupler.     (Signal  Dictionary.) 

they  cross  the  ends  of  movable  bridges.  A  device  for  checking 
the  position  of  lift  bridges  when  closed  is  shown  in  Fig.  90.  A 
is  fastened  to  the  bridge.  The  tumbler  F  has  a  notch  in  it  that 
engages  the  stud  B  when  the  bridge  drops  into  position  and  is 


MECHANICAL  INTERLOCKING 


75 


closed.  E  is  fastened  to  the  bridge  seat.  When  the  bridge  is 
closed,  plunger  D  will  pass  through  the  opening  on  the  back  end  of 
E.  When  the  bridge  is  raised,  the  tumbler  F  pivoted  at  C,  will 
drop  in  front  of  this  opening  stopping  the  movement  of  D  and 
holding  all  signals  and  derails  in  the  normal  position.  As  soon  as 
the  bridge  is  properly  locked,  however,  the  track  may  be  cleared. 
Devices  very  similar  to  this  are  used  to  lock  swing  bridges. 


FIG.  90. — Bridge  lock.     (Signal  Dictionary.) 

49.  Rules. — The  following  rules  prepared  for  the  benefit  of 
train  and  motor  crews  and  signalmen  are  reprinted  from  the 
Proceedings  of  the  Railway  Signal  Association,  1914 11 

"Interlocking  Signal  Rules. — Interlocking  signal  rules  govern  the  use 
of  interlocking  signals. 

"  Interlocking  signals  are  used  to  govern  movements  over  tracks  where 
there  are  switches,  drawbridges,  railroad  crossings  at  grade  and  other 
conditions  affecting  the  movement  of  trains. 

"Hand  signals  must  not  be  accepted  as  authority  to  pass  any  signal 
indicating  STOP,  except  for  switching  movements  when  the  governing 
signal  cannot  be  cleared.  They  must  be  given  by  the  signalman  from 
the  ground,  upon  the  track  for  which  they  are  intended,  and  only  after 
the  train  or  motor  which  is  to  make  the  movement  has  been  stopped, 
and  the  situation  fully  explained  and  understood. 

"Interlocking  Signal  Rules. — For  train  and  motor  crews.  A  signal 
indicating  STOP  must  not  be  passed  except  as  provided  by  the  Rules. 

"  Interlocking  signals  when  at  PROCEED  indicate  the  particular  route 
set  and  show  that  switches  are  locked  for  the  train  to  proceed,  but  not 
that  the  track  is  unoccupied. 

"  Interlocking  signals  indicate  that  a  movement  may  be  made  only 
within  the  limits  of  the  interlocking  plant. 

"Trains  or  motors  stopped  while  within  the  limits  of  an  interlocking 

1  Page  120. 


76  RAILWAY  SIGNALING 

plant,  must  not  move  in  either  direction  until  they  have  received  the 
proper  signal. 

"Interlocking  Signal  Rules. — For  signalmen.  If  necessary  to  stop  a 
train  at  a  point  at  which  clear  signals  have  been  displayed  for  it,  sig- 
nals must  be  changed  to  give  the  STOP  indication,  but  locks  and 
switches  must  not  be  changed  or  signals  cleared  for  a  conflicting  move- 
ment until  the  train  which  had  accepted  the  indication  to  proceed  has 
stopped. 

11 A  switch  or  facing  point  lock  must  not  be  moved  when  any  portion 
of  a  train  or  motor  is  standing  on  or  closely  approaching  the  switch  or 
detector  bar. 

"A  drawbridge  must  not  be  opened  until  proper  signals  have  been 
displayed. 

"During  sleet  or  snow  storms  special  care  must  be  used  in  operating 
switches.  If  the  men  whose  duty  it  is  to  keep  the  switches  in  working 
order  are  not  on  hand  promptly  when  required,  the  fact  must  be  re- 
ported by  wire  (or  telephone)  to  the 

"  During  cold  weather  the  levers  must  be  moved  as  often  as  may  be 
necessary  to  keep  connections  from  freezing. 

"Salt  must  not  be  used  on  interlocked  switches,  or  other  appliances, 
except  on  authority  of 

"Levers  must  be  operated  with  a  careful  uniform  movement.  If  the 
operation  of  a  lever  or  other  apparatus  indicates  a  disarrangement  of 
the  parts,  the  signals  must  be  restored  to  give  the  normal  indication, 
and  an  examination  made  at  once  to  ascertain  if  the  parts  are  in  safe 
and  proper  working  order. 

"Signalmen  must  see  that  lever  is  latched  after  lever  movement  has 
been  completed. 

"Should  it  be  impossible  to  lock  a  facing  point  switch,  the  switch 
must  be  examined  and  spiked  in  proper  position  before  train  is  allowed 
to  pass. 

"When  switches,  signals  and  their  connections  are  undergoing  repairs, 
PROCEED  signals  must  not  be  given  for  movement  over  track  sections 
affected  by  such  repairs,  until  it  has  been  ascertained  that  the  switches 
are  properly  set  and  secured. 

"Signals  must  not  be  cleared  for  trains  to  proceed  except  by  working 
the  lever  provided  for  the  purpose. 

"When  a  switch,  movable-point  frog,  derail,  lock,  detector-bar  or 
switch-locking  circuit  is  inoperative,  the  signalman  will  be  given  notice 
in  writing  by  the  maintainer  and  will  make  record  of  same  on  block 
sheet.  The  signalman  must  know  that  each  switch,  frog,  and  derail 
is  spiked  for  the  desired  route  and,  when  practicable,  locked  with  plunger 
so  that  it  cannot  be  withdrawn,  before  such  route  is  used  by  trains. 
The must  be  notified  promptly  of  the  condition  of  the  appara- 
tus and  the  home  signal  governing  movements  over  the  route  must  indi- 


MECHANICAL  INTERLOCKING  77 

cate  STOP,  and  each  train  must  be  given  a  hand  signal  to  proceed, 
unless  other  instructions  are  received  from  the 

"When  a  switch  or  movable-point  frog  is  spiked  a  man  must  be  sta- 
tioned by  the  section  foreman  or  maintainer  to  see  that  such  parts  are 
properly  set  for  the  route  indicated  by  the  signalman,  before  allowing 
train  to  pass.  The  signalman  must  know  that  switch  or  frog  is  properly 
set  and  secured  for  the  desired  route. 

"When  a  home  signal  is  disconnected,  it  must  be  fastened  in  the  STOP 
position. 

"If  there  is  a  derailment,  or  a  switch  is  run  through,  or  if  any  damage 
occurs  to  the  track  or  interlocking  plant,  the  signals  must  be  restored  to 
give  the  STOP  indication  and  no  train  or  switching  movement  must 
be  permitted  until  all  parts  of  the  interlocking  plant  and  track  liable  to 
consequent  injury  have  been  examined  and  are  known  to  be  in  a  safe 
condition.'* 


CHAPTER  VI 
ELECTRO-PNEUMATIC  INTERLOCKING 

In  electro-pneumatic  interlocking  plants  compressed  air  is  used 
to  throw  switches,  signals  and  derails  operating  them  by  means  of 
cylinders  whose  valves  are  controlled  by  electricity.  As  the 
action  is  quicker  than  is  the  case  in  the  mechanical  and  electrical 
plants,  the  system  finds  its  best  application  in  large  terminals,  in 
subway  and  elevated  lines,  and  in  other  places  where  there  is 
frequent  traffic. 


FIG.  91.— South  Station,  Boston,  Mass. 

50.  Air  Supply. — At  points  where  such  plants  are  likely  to  be 
installed  there  is  frequently  an  adequate  supply  of  air  already 
available  that  needs  only  to  be  piped  to  the  immediate  places 
where  it  is  to  be  used.  In  case  no  such  supply  is  convenient  it 
becomes  necessary  to  install  a  compressor,  operated  either  by  a 
gasoline  engine  or  by  an  electric  motor.  The  air  is  pumped  into 
storage  reservoirs  to  maintain  an  adequate  supply,  the  pressure 

78 


ELECTRO-PNEUMATIC  INTERLOCKING 


79 


of  which  usually  averages  about  75  Ib.  a  square  inch.     A  typical 
plant  is  illustrated  by  Fig.  92. 

After-coolers  of  the  water  and  air-cooled  type  are  usually 
employed  to  reduce  the  temperature  of  the  air  to  normal  after  it 
has  passed  through  the  compressor.  The  storage  tanks  provided 
for  the  air  are  usually  set  low  enough  to  collect  the  moisture  that 
results  from  condensation,  thus  eliminating  the  danger  of  the 
freezing  of  the  plant  in  the  winter.  The  air  pipes  that  connect 
with  the  storage  supply  and  furnish  the  trunk  line  of  the  piping 
system  are  usually  about  2  in.  in  diameter.  The  branch  pipes 
are  usually  %  in.  in  diamteter  with  J^-in.  connections  to  switches 
and  signals.  On  account  of  the  flexibility  and  vibration  of  the 


.dufvmahcConfrot 
.    \ofliotorby 
'  '</(  Air  Press  ure 


Pinion 


FIG.  92. — Diagram  of  typical  air  compressing,  cooling  and  distributing  system 
for  electro-pneumatic  interlocking. 


track,  the  connection  to  switches  is  usually  made  with  an  armored 
hose. 

The  pipe  is  generally  galvanized,  and  where  it  is  laid  across 
the  tracks  is  placed  a  few  inches  beneath  the  surface  of  the 
ground;  where  the  pipe  is  laid  parallel  with  the  tracks,  it  is  usually 
supported  a  few  inches  above  the  ground  on  wooden  stakes  or 
concrete  piers.  Usually  two  routes  are  provided  to  each  switch 
and  signal  to  insure  an  air  supply  in  case  of  failure  in  some  part  of 
the  pipe  line.  Gate  valves  are  located  in  the  mains  and  stop- 
cocks in  the  branches  in  order  to  be  able  to  shut  off  the  air  and  cut 
out  a  section  should  it  become  necessary  to  repair  a  pipe  or 
break  a  connection  to  a  switch  or  signal. 

Expansion  in  the  mains  is  provided  for  by  bends  or  by  sliding 
expansion  joints.  Branch  pipes  should  come  out  of  the  tops  of 


80  RAILWAY  SIGNALING 

mains,  thereby  eliminating  the  possibility  of  having  water  drawn 
over  if  the  main  should  not  be  properly  drained.  An  auxiliary 
air  reservoir  is  usually  provided  near  each  switch  or  signal  to 
furnish  an  immediate  supply  of  air  and  to  provide  a  sump  for  any 
water  that  may  have  collected  in  the  pipe.  A  strainer  is  placed 
in  the  line  where  it  joins  the  operating  equipment  to  clear  the  pipe 
of  any  moisture  or  sediment  that  may  accumulate  while  the  air  is 
passing  through.  All  of  the  reservoirs  along  the  line  are  so  con- 
structed that  the  water  may  be  blown  out  as  often  as  desired. 

51.  Electricity. — The  supply  of  electricity  for  most  electro- 
pneumatic  plants  is  furnished  by  storage  cells,  although  a  few  have 
been  built  for  110- volt  alternating  current.     Six  or  seven  cells 
of  the  lead  type  or  12  of  the  Edison,  furnishing  approximately  12 
volts,  constitute  the  main  battery.     The  usual  practice  is  to  have 
a  gasoline  engine  or  an  electric  motor  drive  a  generator  to  charge 
the  batteries.     To  guard   against  failures,   this  equipment   of 
engine,  generator  and  batteries  is  generally  duplicated.     The  best 
place  to  install  such  equipment  is  in  the  lower  part  of  the  tower 
where  the  signalmen  can  take  care  of  it. 

52.  General  Sequence  in  Power  Interlocking. — From  consid- 
erations of  safety  it  is  fundamental  in  power  interlocking  that  the 
steps  involved  in  the  throwing  of  a  switch  and  the  clearing  of  a 
signal  should  take  place  in  the  following  sequence: 

1.  In  providing  assurance  that  conditions  are  right  for  the 
throwing  of  the  switch.     The  mechanical  locking  insures  that 
no  conflicting  routes  are  set  up  and  that  no  signals  are  cleared  for 
movement  over  the  switch.     The  detector  locking,  which  electri- 
cally locks  the  switch  levers,  insures  that  no  train  is  within  a 
certain  distance  of  the  switch.     Thus  the  lever  is  mechanically 
and  electrically  unlocked  if  conditions  are  right.     When  detector 
locking  is  not  installed,  detector  bars  operated  by  the  switch 
movement  provide  mechanically  against  movement  of  the  switch 
while  a  train  is  over  the  detector  bar. 

2.  In  making  a  preliminary  lever  movement  which  mechan- 
ically locks  conflicting  levers,  and  effects  circuit  changes  which 
cause  the  switch  to  be  thrown. 

3.  In  receiving  an  indication  that  the  switch  has  been  thrown 
and  locked. 

4.  In  completing  the  lever  stroke,  which  frees  the  mechanical 
locking  for  other  lever  movements. 

5.  In  throwing  the  signal  lever  which  clears  the  signal.     No 


ELECTRO-PNEUMATIC  INTERLOCKING  81 

indication  is  required  that  the  signal  actually  clears  since  it 
would  not  be  an  unsafe  condition  if  it  should  fail  to  clear. 

After  the  train  has  accepted  the  signal  and  passed  through  the 
route,  it  may  be  desired  to  change  the  route  for  other  train  move- 
ments. In  order  to  do  so  it  is  necessary  to : 

1.  Restore  the  signal  to  stop  by  preliminary  lever  movement. 

2.  Receive  an  indication  that  the  signal  has  gone  to  the  stop 
position. 

3.  Place  the  lever  in  full  normal  position,  thus  freeing  the 
mechanical  locking  for  other  lever  movements. 

A  description  of  the  different  parts  of  the  electro-pneumatic 
system  follows  with  an  explanation  of  how  each  functions  in  the 
sequence  outlined  above. 

53.  Interlocking  Machine. — Figure  93  shows  a  Model  14  elec- 
tro-pneumatic interlocking  machine.  The  operating  levers  are 


FIG.  93. — Electro-pneumatic  interlocking  machine. 

arranged  in  a  row  across  the  front  of  the  machine  and  are  num- 
bered from  left  to  right.  Those  turned  upwards  are  switch  levers 
and  bear  odd  numbers,  while  those  hanging  vertically  downwards 
are  signal  levers  and  bear  even  numbers.  In  its  normal  position 
the  switch  lever  stands  30  degrees  to  the  left  of  the  vertical, 
and  when  reversed  it  stands  30  degrees  to  the  right  of  the  vertical, 
moving  through  an  angle  of  60  degrees.  One  switch  lever  may 
control  one,  two  and  sometimes  three  switches,  derails  or  movable 
point  frogs.  The  signal  lever  points  vertically  downwards 
when  normal;  thrown  30  degrees  to  the  left  it  serves  to  clear  its 
corresponding  signal  or  the  selected  one  of  a  group  of  signals; 
thrown  30  degrees  to  the  right  it  clears  another  given  signal  or 
selected  one  of  a  group,  for  train  movement  in  the  opposite  di- 


82 


RAILWAY  SIGNALING 


rection.  All  signals  that  may  be  controlled  by  a  given  lever, 
however,  must  be  those  that  govern  movements  over  a  common 
section  of  track.  The  ability  to  control  more  than  one  switch, 
or  more  than  one  signal,  from  a  given  lever  saves  a  great  many 


FIG.  94. — Electro-pneumatic  interlocking  machine.     Case  removed. 

levers,  makes  it  possible  to  erect  a  smaller  and  cheaper  tower,  and 
reduces  the  number  of  operators  required  on  large  plants. 

Each  lever  of  the  machine  is  fastened  to  a  horizontal  shaft  that 
extends  from  the  front  to  the  back  of  the  machine,  and  is  equipped 


FIG.  95.— Electro-pneumatic  interlocking  machine.     Rear  view. 

with  a  latch  that  is  operated  by  turning  the  handle.  As  the  lever 
is  rotated,  the  latch  moves  over  a  notched  quadrant  on  the  front 
of  the  machine.  In  order  to  move  a  lever  it  is  first  necessary  to 
turn  the  handle  and  thus  to  raise  the  latch  out  of  its  notch. 


ELECTRO-PNEUMATIC  INTERLOCKING 


83 


The  front  portion  of  each  lever  shaft  operates  one  of  the  lock- 
ing bars  of  a  mechanical  locking  bed,  as  shown  in  Fig.  98.  This 
locking  bed  is  similar  to  that  used  on  a  Saxby  and  Farmer  ma- 
chine, except  that  it  is  constructed  on  a  smaller  scale.  A  segmen- 
tal  gear  fitted  to  the  shaft  meshes  in  a  rack  cut  on  the  under  side 
of  the  locking  bar.  As  the  shaft  is  rotated  the  bar  is  shifted. 
The  rear  section  of  the  shaft  carries  the  segments  that  engage  the 


Clamp  -. 


MC(.HANH.AL  LUinmb,        . . 


Lever 
Shaft 
\  Driver 
\  lakh  Depressor 
Quadrant 


Hard  Rubber  Roller 
Quick  Switch 


Contact  Springs 
Supported  by 
Insulated  Plate 
Which  is,  not  Show 


Toggle  of 
Quick  Switch 


Driver  for  Chick  Switch 
Coupling-^' 


.Locking 
Segment 

Hormal 

••''Indication 

Latch 


•  Hormal  Indication 
Magnet 


.Lower Section  of  Rollers 


Arms  and  Links,  for 
Driving  Lower  Section 
of  Any  Roller  of  the 
Machine  from  Another 
Lever  When  Required:. 


FIG.  96. — Switch  lever  complete. 

indication  latches.  These  latches  are  dropped  and  locked  by 
gravity  and  are  raised  and  unlocked  by  the  armatures  of  the 
electro-magnets.  Projections  on  the  segments  are  engaged  by 
the  latches  unless  the  magnets  are  energized  at  the  proper  time. 
There  are  two  indication  magnets  for  each  switch  lever,  the 
normal  and  the  reverse.  The  segments  are  arranged  to  provide 
detector  locking  and,  after  the  preliminary  movement,  to  restrict 
further  lever  movement  until  the  switch  indication  has  been  re- 
ceived.- Figure  97  gives  a  diagram  of  a  switch  lever  and  a  re- 


84 


RAILWAY  SIGNALING 


verse  indication  segment.  Each  signal  lever  has  one  magnet, 
often  called  the  lock  magnet.  Its  function  is  to  prevent  the  plac- 
ing of  the  signal  lever  in  the  full  normal  position  until  the  indica- 
tion is  received  that  the  signal  has  gone  to  the  stop  position. 
Figure  98  shows  a  signal  lever  in  its  "L"  (reversed)  position. 
Figure  99  gives  a  diagram  of  its  positions  and  operations. 


FIG.  97. — Diagram  of  a  switch  lever  and  its  operation. 

As  shown  in  Figs.  96  and  98,  a  set  of  bevel  gears  near  the  middle 
of  the  lever  shaft  serves  to  transmit  motion  to  a  vertical  shaft. 
This  vertical  shaft  forms  a  part  of  the  "combination"  or  circuit 
controller  that  is  used  to  govern  the  movements  of  switches  and 
signals.  It  is  encased  in  a  hard  rubber  roller  upon  which  are 
mounted  phosphor  bronze  bands  that  turn  between  flat  phosphor 
bronze  springs  extending  out  from  a  vertical  plate  of  moulded 
insulating  material.  These  rollers  have  a  number  of  fine  longi- 
tudinal saw-cuts  which  receive  and  hold  the  turned-in  ends  of  the 


ELECTRO-PNEUMATIC  INTERLOCKING 


85 


contact  bands  as  illustrated  in  Fig.  97d.  The  contact  bands  as 
well  as  the  contact  springs  are  made  in  several  lengths  so  that  it 
is  possible  to  arrange  a  circuit  to  open  or  close  at  any  desired 
position  of  the  operating  lever.  The  adjustment  of  these  circuit 
controllers  is  made  much  easier  by  the  fact  that  the  roller  is  con- 
structed to  turn  through  twice  as  many  degrees  as  the  lever  shaft 
by  the  ratio  of  the  bevel  driving  gears. 


BevelGear 

Drive  Ratio 

I  to  2 


Clamp 


'Segment 
Latch 


Lock  Magnet 


Con-fact  Springs 
Supported  by 
Insulated  Plate 
Which  is  not  Shown 


Lower  Section 
of  Roller  C 

Here  Driven 
by  So  Her  A 

Arms  and  Links 
for  Dn  ving  Lower 
Section  of  Any  Roller 
of  the  Machine  from 
Another  Lever  Whem 
Required 

FIG.  98. — Signal  lever  complete. 

In  an  earlier  type  of  the  machine,  the  contact  rollers  were 
made  an  intermediate  part  of  the  lever  shaft;  and  the  insulating 
plate  supporting  the  contact  springs  was  held  in  a  horizontal 
position  below  it.  This  machine  is  called  the  horizontal  roller 
type,  while  the  Model  14  machine  is  known  as  the  vertical  roller 
type. 

On  the  end  of  each  switch  roller  is  a  hard  rubber  collar,  or 
sleeve,  on  which  are  mounted  two  contact  bands  that  operate 
between  springs  mounted  on  the  same  insulating  plate.  This 
collar  or  sleeve  does  not  turn  with  the  shaft  until  the  lever  has 


86 


RAILWAY  SIGNALING 


moved  through  an  angle  of  50  degrees,  being  held  in  its  original 
position  by  a  toggle  spring.     When  the  shaft  has  turned  five- 


tb)  co 

FIG.  99. — Diagram  of  a  signal  lever  and  its  operation. 


TERMINAL  SCRLWS 


'CHANNEL  BAR   CARRY1NC 

BINAT10N  PLATES  AND 
BEARINGS  TOR   ROLLERS 


FIG.  100. — Rollers,  contact  springs  and  quick  switches. 

sixths  of  its  throw,  however,  this  collar  is  also  forced  to  turn,  and 
as  its  toggle  passes  dead  center  it  snaps  over  to  its  opposite  ex- 


ELECTRO-PNEUMATIC  INTERLOCKING 


87 


treme  position.  This  arrangement  is  called  the  "quick  switch," 
and  is  illustrated  in  Figs.  96,  97 'd,  and  100. 

The  working  parts  of  the  machine  are  enclosed  in  an  enameled 
steel  case  to  prevent  the  accumulating  of  dust  and  the  tampering 
with  the  parts  by  unauthorized  persons. 

54.  Mechanism  for  Throwing  Switches  and  Derails. — The 
switches  are  operated  by  means  of  switch  and  lock  movements 
similar  to  the  ones  used  in  mechanical  interlocking,  the  actuating 
power,  however,  being  compressed  air.  The  piston  rod  of  the 
air  cylinder  connects  directly  with  the  slide  bar  of  the  switch  and 


(«— 14--+I. 

FIG.   101. — Electro-pneumatic  switch  and  lock  movement. 

lock  movement,  as  indicated  by  Fig.  101.  The  stroke  of  the  pis- 
ton rod  and  of  the  switch  and  lock  movement  is  12  in.  The  first 
2  in.  of  the  stroke  unlocks  the  switch  and  throws  the  detector 
bar,  the  next  8  in.  throws  the  switch,  and  the  last  2  in.  locks 
it  in  its  new  position. 

The  switch  cylinder  and  piston  operate  very  much  like  the 
cylinder  and  piston  on  a  steam  engine.  On  the  side  of  the  switch 
cylinder,  but  sometimes  separately  mounted,  is  a  "D"  slide 
valve,  Figs.  102  and  103,  which  opens  and  closes  the  inlet  and 
exhaust  ports  to  the  cylinder.  This  slide  valve  is  driven  by  two 
small  shifting  pistons,  one  on  each  side,  impelled  by  compressed 
air.  The  flow  of  air  behind  these  pistons  is,  in  turn,  controlled 


88 


RAILWAY  SIGNALING 


by  the  normal  and  reverse  electro-magnets.  Provision  is  made 
for  locking  the  slide  valve  by  a  lock  that  is  operated  at  right  angles 
to  the  motion  of  the  slide  valve,  and  is  actuated  by  a  third  piston. 
Air  pressure  behind  the  lock  piston  is  controlled  by  the  lock 
magnet.  The  lock  piston  also  opens  and  closes  a  valve  which 
controls  the  supply  of  air  to  the  valve  body.  Thus  it  is  seen 
that  the  switch  valve  has  three  magnets,  normal,  reverse  and 
lock.  To  throw  a  switch  it  is  necessary  to  energize  the  lock 
magnet  in  order  to  unlock  the  slide  valve  and  admit  air  to  the 


FIG.  102. — Switch  valve  and  magnets. 

valve  body,  and  to  deenergize  one  of  the  control  magnets  and 
energize  the  other  in  order  to  shift  the  slide  valve.  When  the 
controlling  lever  is  in  full  normal  or  reverse  position,  current  is 
maintained  on  the  corresponding  control  magnet,  but  is  cut  off 
from  the  lock  magnet. 

The  operation  of  an  electro-pneumatic  magnet  may  be  under- 
stood from  an  inspection  of  Fig.  104,  which  shows  the  type  used 
on  a  signal.  Between  the  armature  and  the  coil  are  three  short 
springs  that  keep  the  armature  raised  when  the  magnet  is  not 
energized.  Attached  to  the  armature  and  running  down  inside 
the  coil  is  the  armature  stem,  the  lower  end  of  which  is  so  bevelled 
as  to  seat  itself  and  hold  the  exhaust  post  closed  when  the  mag- 


ELECTRO-PNEUMATIC  INTERLOCKING 


GTUNOCR 


CHECK  VU.VE. 
NAJR  INUCT. 


OIL  PLUG. 


CYLINDER  HEAD.- 

UNLOCK  PISTO 

LOCK  PISTON. 
LOCKING  TAPPET, 
STUFFING  Box 


EXHAUST  PORT. 
%  ^-EXHAUST  VALVE. 
W~ INLET  VALVE. 

-VALVE. 

HIFTING  PlSTON. 


STRAINER 

IR  INLET. 
FIG.  103,  PART  1. — Switch  valve  and  magnets. 


J 


90 


RAILWAY  SIGNALING 


net  is  energized.  The  lower  end  of  this  stem  engages  the  stem 
of  a  pin  valve.  Air  under  pressure  comes  into  the  air  supply 
pipe.  When  the  coils  are  energized  the  pin  valve  is  unseated 
and  the  exhaust  valve  is  closed,  allowing  air  to  pass  from  the  air 
supply  pipe  directly  into  the  pipe  leading  to  the  cylinder. 


OIL  PL 


CYLINDER  HEAD 
UNLOCK  PISTON 

LOCK  PlSTONr 

LOCKING  TAPPET, 
STUFFING  Box. 


-EXHAUST  PORT. 
EXHAUST  VALVE. 
INLET  VALVE. 

D-VM.VE. 
HIFTING  PISTON. 


STRAINI 

UR  INLET. 
FIG.   103,  PART  2. — Switch  valve  and  magnets. 

55.  Indication  Circuit  Controller. — Mounted  on  the  switch 
movement  and  actuated  by  a  cam  plate  attached  to  the  slide  bar 
is  the  indication  circuit  controller,  Fig.  105.     It  is  enclosed  in  a 
cast  iron  case,  and  consists  of  slides  of  insulating  material  bearing 
contact  springs  that  move  between  contact  points  mounted  on 
either  side.     The  motion  transmitted  to  the  slides  is  such  that 
one  makes  its  movement  before  the  switch  is  fully  unlocked,  and 
remains  stationary  while  the  switch  is  being  thrown;  the  other 
makes  its  movement  after  the  switch  is  locked  in  the  opposite 
position. 

56.  Indication  Relays. — Located  in  the  tower  is  one  polarized 
relay  for  each  switch  lever.     A  pair  of  small  wires  connect  each 
relay  to  a  switch  circuit  controller.     When  the  switch  is  normal 


ELECTRO-PNEUMATIC  INTERLOCKING 


91 


and  locked,  current  of  a  certain  polarity  is  fed  to  these  wires 
through  the  indication  circuit  controller;  when  the  switch  is 


DJUSTMENT 

-ARMATURE 

BRASS  TUBE 
.—OUTER  POLE 
INNER  POLE 
INSULATION 
HELIX 
ARX 


CLAMP 

AJR SUPPLY- 
FIG.   104. — Cross-section  of  pin  valve. 


unlocked  or  open,  these  wires  are  disconnected  from  their  source 
of  energy  and  are  connected  together;  when  the  switch  is  reversed 


FIG.  105. — Pole-changing  indication  circuit  controller. 

and  locked,  current  of  a  polarity  opposite  to  that  used  for  normal 
indication  is  fed  to  the  indication  wires.     Thus  the  relay  in  the 


92 


RAILWAY  SIGNALING 


tower  is  made  to  repeat  the  position  of  the  switch.  Unless  the 
switch  is  fully  locked  the  relay  contacts  will  be  open.  When 
the  switch  is  normal,  one  set  of  polar  contacts  on  the  relay  is 


closed;  when  the  switch  is  reversed,  the  other  set  of  polar  contacts 
is  closed.  Current  for  picking  up  the  switch  lever  indication 
magnets  is  taken  locally  through  both  neutral  and  polar  con- 
tacts of  the  polarized  relays.  Thus  the  indication  magnets  can 


ELECTRO-PNEUMATIC  INTERLOCKING 


93 


receive  current  only  when  the  relay  is  picked  up  and  the  proper 
polar  contacts  are  closed. 

The  quick  switch  previously  mentioned  serves  to  close  the  local 
indication  circuit  to  that  magnet  which  should  be  next  picked 


UJl 


1 

A 

I 


up  and  to  open  the  circuit  to  the  other  magnet.  As  normal  indi- 
cation is  received  and  the  lever  stroke  completed,  the  quick 
switch  opens  that  circuit  and  closes  the  circuit  to  the  reverse 
indication  magnet,  which  will  be  the  next  one  to  be  picked  up. 


94  RAILWAY  SIGNALING 

57.  Detector   Locking. — At   the   extreme    end   of   the  lever 
stroke,  the  magnet  which  has  been  disconnected  by  the  quick 
switch  from  its  source  of  current  coming  through  the  indication 
relay,  is  connected  by  the  "X"  or  "  Y"  springs  to  another  source 
of  energy  controlled  by  the  track  relay  of  that  section  in  which 
the  switch  is  located.     Thus  the  indication  magnets  also  serve  as 
detector  magnets,  for  the  levers  in  full  normal  or  full  reverse 
position  are  locked  in  place  unless  the  corresponding  magnet  can 
be  energized.     A  switch  could  not  be  thrown  with  a  train  in  that 
particular  track  section  because  the  track  relay  would  be  open, 
interrupting  the  flow  of  current.     The  current  for  this  circuit  is 
also  passed  through  a  normally  open  contact  actuated  by  the 
lever  latch  so  that  the  magnet  is  not  continually  using  current. 

58.  "SS"  Control. — Current  from  the  signal  levers  for  clearing 
the  different  signals  is  carried  over  contacts  on  the  indication 
relays  of  those  switches  in  the  route  governed.     This  arrangement 
provides  assurance  in  addition  to  the  mechanical  locking  that  all 
switches  are  properly  set  in  order  to  get  a  clear  signal  and  makes 
certain  that  no  switches  have  been  improperly  set  by  hand  after 
the  indication  was  received,  a  point  which  would  not  be  checked 
by  the  mechanical  locking. 

59.  Throwing  a  Switch. — When  the  lever  is  in  its  normal  or 
reverse  position  and  its  latch  is  lifted,  it  completes  the  circuit 
from  the  track  relay  through  the  latch  contact  energizing  the 
magnet  of  the  normal  or  reverse  indication  segment  latch,  pro- 
vided there  is  no  train  to  short-circuit  the  track  relay  and  drop 
its  armature,  as  shown  in  Fig.  106.     This  unlocks  the  lever  and 
allows  it  to  be  rotated.     In  following  the  cycle  of  throwing  a 
switch,  the  switch  is  considered  to  be  in  its  normal  position  and 
will  be  thrown  from  normal  to  reverse. 

When  the  lever  shaft  has  been  turned  10  degrees  to  the  right, 
the  contact  is  made  on  the  hard  rubber  roller  that  energizes  the 
lock  magnet  at  the  switch  cylinder,  unlocking  the  slide  valve  in 
the  cylinder.  The  further  rotation  of  the  lever  shaft  up  to  a 
total  angle  of  37J^  degrees  makes  other  contacts  on  the  hard 
rubber  roller,  deenergizing  the  normal  magnet  and  at  the  same 
time  energizing  the  reverse  magnet.  This  permits  the  air  to 
escape  from  behind  one  of  the  small  pistons  and  to  exert  a  pres- 
sure behind  the  other  so  as  to  move  the  slide  valve  and  admit  air 
behind  the  piston  of  the  switch  cylinder.  This  pressure  causes 
the  piston  to  travel  the  length  of  its  stroke  throwing  the  switch 


ELECTRO-PNEUMATIC  INTERLOCKING 


RAILWAY  SIGNALING 


ELECTRO-PNEUMATIC  INTERLOCKING 


97 


and  locking  it  by  means  of  the  switch  and  lock  movement.  When 
the  switch  is  thrown  to  its  proper  position,  the  circuit  is  completed 
through  the  switch  indication  circuit  controller  picking  up  and 
reversing  the  polarized  indication  relay  and  energizing  the  reverse 
indication  magnet,  thereby  raising  the  segment  latch  and  allow- 
ing the  lever  to  finish  its  stroke  to  the  extreme  right.  The  lock 
magnet  is  now  deenergized,  but  the  reverse  control  magnet  re- 
mains energized  until  the  switch  points  are  thrown  back. 

When  the  movement  of  the  lever  is  being  completed,  it  operates 
the  quick  switch,  which  opens  the  indication  circuit  for  the  re- 
verse indication  magnet  and  closes  the  corresponding  circuit  for 


LATCH  CIRCUIT  CONTROLLER- 


DETECTOR  > 

THROUGH  NECESSARY  TRACK  REL 

AND  ROUTE  LOCKING  RELAYS 


NORMAL  CONTROL  MAGNET, 
REVERSE  CONTROL  MAGNET 


NDICATION  CIRCUIT 


=d 


12  VOLT  D  C  POWER  MAINS  FOR  THE  COMPL 


FIG.  110. — Diagram   of   complete   control,    indication   and   locking   circuits   for 
single  switch  with  D.C.  indication. 

the  normal  magnet,  although  the  latter  magnet  cannot  receive 
any  current  until  the  polarized  relay  has  responded  to  the  next 
movement  of  the  switch.  As  the  quick  switch  opens  the  indi- 
cation circuit,  the  "Y"  springs  close  the  circuit  from  the  track 
relay  to  the  reverse  indication  magnet  through  the  latch  contact. 
When  the  latch  drops  into  its  notch,  the  latch  contact  opens,  thus 
leaving  the  magnet  on  open  circuit  to  economize  on  current. 
Should  it  later  be  desired  to  move  the  switch  back  to  normal  it 
would  first  be  necessary  to  raise  the  lever  latch  which  closes  the 
detector  circuit  for  the  reverse  magnet  in  order  to  raise  the  indi- 
cation latch  and  unlock  the  lever.  If  a  train  is  on  the  track 
circuit,  the  track  relay  contacts  will  be  open,  the  magnet  cannot 
be  picked  up  and  the  lever  is  locked  in  place.  Complete  move- 

7 


98 


RAILWAY  SIGNALING 


ment  from  reverse  to  normal  is  exactly  similar  to  that  described 
above. 

Only  during  the  time  when  the  lock  magnet  on  the  switch  is 
energized  is  air  admitted  through  the  slide  valve  into  the  switch 
cylinder  and  the  pressure  maintained.  When  the  lock  magnet 
is  deenergized  not  only  does  it  lock  the  slide  valve,  but  also  it  cuts 
off  the  supply  of  air  to  the  slide  valve  chamber  and  consequently 
to  the  switch  cylinder.  This  arrangement  avoids  the  waste  of  air 
that  would  occur  by  leakage  if  the  pressure  should  be  maintained 


FIG.  111. — Two-arm  electro-pneumatic  dwarf  signal. 

constantly  in  the  cylinder.  Figure  110  is  a  diagram  showing 
complete  control,  indication,  and  locking  circuits  for  a  single 
switch  with  direct  current  indication. 

60.  Signal  Operating  Mechanism.— The  air  cylinder  that 
operates  a  high  signal  is  usually  placed  at  the  base  of  the  pole. 
The  up-and-down  signal  rod  operates  inside  the  pole  and  is 
connected  to  the  piston  of  the  air  cylinder  by  a  balance  lever.  As 
the  spectacle  casting  is  counterweighted  causing  the  signal  to  go 


ELECTRO-PNEUMATIC  INTERLOCKING 


99 


to  stop  by  gravity,  the  air  is  used  only  to  clear  the  signal,  thus 
requiring  merely  a  single  acting  cylinder.  An  electro-magnet 
fastened  to  the  signal  cylinder  controls  the  movement  of  the  air. 
There  is  a  circuit  breaker  on  the  signal  cylinder  that  gives  an 
indication  only  when  the  signal  is  at  normal.  There  is  no  indi- 
cation when  the  signal  is  cleared.  The  stroke  of  the  piston  is 
4J4  in.  and  the  diameter  of  the  cylinder  is  3  in. 

In  the  construction  of  the  dwarf  signal,  shown  in  Fig.  Ill,  the 
up-and-down  rod  is  attached  directly  to  the  signal  cylinder;  the 
piston  remains  stationary.  As  the  air  is  admitted  to  the  cylinder 
by  means  of  an  electro-magnet,  the  cylinder  itself  moves  upwards 


FIG.  112. — Diagram  of  complete  signal  control  and  indication  circuits;  lever 
and  signals  normal. 

clearing  the  signal,  but  compressing  a  coil  spring  on  the  up-and- 
down-rod.  As  soon  as  the  air  is  released,  the  coil  spring  restores 
the  signal  to  normal.  A  pair  of  contact  springs  placed  on  the  side 
of  the  air  cylinder  acts  as  a  circuit  breaker  and  completes  the 
circuit  when  the  signal  is  normal.  The  stroke  of  the  dwarf  signal 
is  2J4  in.  The  diameter  of  the  piston  is  3  in.  the  same  as  the 
high  signal. 

61.  Operating  a  Signal. — For  the  purpose  of  explanation  it  will 
be  assumed  that  the  signal  is  in  its  normal  position.  The  lever 
may  be  turned  to  the  left  or  right  as  the  case  may  require. 


100 


RAILWAY  SIGNALING 


After  it  has  been  rotated  through  an  angle  of  about  25  degrees, 
contact  is  made  by  the  bronze  band  on  the  hard  rubber  roller 
completing  the  circuit  to  the  electro-magnet  at  the  signal  cylinder 
admitting  the  air  and  moving  the  piston  rod  to  clear  the  signal. 
To  reverse  the  operation,  the  lever  is  rotated  a  short  distance 
thereby  breaking  the  circuit  to  the  electro-magnet  at  the  signal 
cylinder  and  releasing  the  air  that  holds  the  signal  clear.  Before 
it  can  be  restored  to  normal  the  signal  must  go  to  the  stop  position 
so  as  to  make  contact  with  the  circuit  breaker  to  unlock  the  lock 
magnet  on  the  lever  shaft.  Figures  112  and  113  show  a  signal 
lever  and  its  circuits. 


Switch  Lever 

Signal  Lever 
to  Right 

FIG.  113. — Diagram  of  complete  signal  control  and  indication  circuits;  lever 
and  one  signal  reversed. 

The  electro-magnets  that  control  the  segment  latches  on  the 
back  end  of  the  lever  shaft  are  wound  to  a  resistance  of  130  ohms. 
As  these  are  energized  for  very  short  periods  during  the  rotation 
of  the  levers,  their  total  consumption  of  current  is  comparatively 
small.  The  electro-magnets  on  the  switches  and  signals  are 
energized  for  longer  periods,  however,  and  consume  more  cur- 
rent. One  magnet  on  the  switch  cylinder  is  energized  all  the  time 
and  the  magnet  on  the  signal  is  energized  during  the  time  it  indi- 
cates proceed.  To  reduce  the  amount  of  current  as  much  as 
consistent,  signal  coils  are  wound  to  a  resistance  of  400  ohms. 
No.  16  wire  is  used  for  conductors  except  the  two  mains,  where 


ELECTRO-PNEUMATIC  INTERLOCKING  101 

not  over  No.  9  is  necessary.  The  five  wires  leading  to  a  switch 
are  put  in  a  cable  with  different  colors  for  each  wire.  These  wires 
are  laid  in  trunking  to  protect  them  from  the  weather  and  from 
mechanical  wear. 

62.  Advantages. — As  the  main  function  of  the  levers  in  an 
electro-pneumatic  plant  is  to  make  and  break  circuits,  the  lever 
equipment  is  much  lighter  and  much  more  compact  than  that  in 
a  mechanical  plant;  consequently,  it  requires  much  less  space  to 
house  the  plant  and  fewer  men  to  operate  it. 

As  the  connections  between  the  levers  and  the  functions  they 
operate  are  made  by  wires,  a  great  deal  of  space  is  saved  for  build- 
ings and  tracks  that  would  be  required  for  pipes  if  mechanical 
equipment  should  be  used.  It  is  easily  adapted  to  any  kind  of 
yard  conditions  where  there  are  sharp  curves,  complicated 
switches,  and  movable  point  frogs. 

Since  the  movements  of  the  switches  and  signals  can  be  very 
quickly  made,  train  movements  in  busy  terminals  are  subjected 
to  a  minimum  of  delay  on  account  of  interlocking. 

The  many  ways  of  checking  and  locking  and  guarding  against 
plant  failure  and  consequent  danger  promote  safety  in  train 
operation. 

On  account  of  the  adaptability  of  the  plant,  more  signals  and 
switches  can  be  thrown  with  a  single  lever  than  can  be  done  with 
a  mechanical  plant. 


CHAPTER  VII 
ELECTRIC  INTERLOCKING 

The  source  of  power  used  to  operate  an  electric  interlocking 
plant  generally  consists  of  110- volt  storage  battery  with  its 
charging  unit.  During  the  past  20  years,  direct  current  has  been 
used  almost  exclusively  to  operate  electric  interlocking,  but  a  few 
plants  have  been  installed  that  employ  alternating  current.  The 
interlocking  plant  is  such  a  vital  part  of  a  railway  system  that  an 
unfailing  source  of  power  such  as  a  storage  battery  is  generally 
considered  necessary.  The  levers  in  the  interlocking  machine 
are  operated  by  hand,  but  their  only  purpose  is  to  make  and 
break,  in  the  proper  sequence,  contacts  in  the  circuits  that  supply 
current  to  the  motors  which  operate  derails,  switches  and  signals. 
A  large  percentage  of  plants  now  being  installed  are  electric,  for 
electric  interlocking  is  well  adapted  to  the  operation  of  all  types 
of  yards,  terminals  and  crossings  under  every  traffic  and  climatic 
condition. 

THE  GENERAL  RAILWAY  SIGNAL  COMPANY  SYSTEM1 

63.  Electricity. — The  current  for  operating  the  switches  and 
signals  of  the  General  Railway  Signal  plant  is  generally  furnished 
by  a  110- volt  storage  battery  which  is  composed  of  57  cells  of  the 
chloride  accumulator  (lead)  type  or  92  cells  of  the  Edison  type. 
Where  the  chloride  accumulator  type  is  used,  the  battery  should 
have  sufficient  ampere-hour  capacity  to  operate  the  plant  seven 
or  eight  days,  and  where  the  Edison  type  is  used  the  capacity 
should  be  sufficient  to  operate  the  plant  four  or  five  days.     It 
is  customary  to  provide  space  in  the  lower  part  of  the  interlocking 
tower  for  the  storage  battery  with  its  charging  unit.     The  battery 
is  usually  charged  by  a  generator  driven  by  an  electric  motor  or 
by  a  gasoline  engine,  but  in  a  few  cases  it  is  charged  by  a  mercury 
arc  rectifier. 

64.  Operating  Switchboard. — Figure  114  represents  an  oper- 
ating switchboard  where  all  functions  in   the   plant  are  con- 
trolled by  a  single  circuit  breaker.     The  apparatus  mounted  on 

1  General  Railway  Signal  Handbook,  "Electric  Interlocking." 

102 


ELECTRIC  INTERLOCKING 


103 


the  board  consists  of  the  cross  protection  circuit  breaker  with 
its  indicating  red  lamp,  a  polarized  relay,  a  ground  lamp  and 
switch,  and  a  voltmeter  and  ammeter. 


FIG.  114. — Operating  switchboard. 

65.  Interlocking  Machine. — Figure  115  represents  a  per- 
spective of  a  Model  2  interlocking  machine,  while  Fig.  116 
shows  a  section  parallel  with  the  levers.  This  type  of  machine 


104 


RAILWAY  SIGNALING 


FIG.  115.— Model  2  unit  lever  type  interlocking  machine.     Lake  Street  Interlock- 
ing Plant,  Chicago  Terminal,  C.  &  N.  W.  R'y. 


LOCKING  PLATES 


FIG.  116.— Cross   section   of   Model   2   unit   lever   type  interlocking  machine. 


ELECTRIC  INTERLOCKING 


105 


requires  less  room  to  house  than  the  mechanical  and  fewer  op- 
erators to  manipulate  the  levers.  There  are  also  more  checks 
to  guard  against  failure,  for  it  has  both  electrical  and  mechanical 
locking  with  provision  for  safeguarding  against  false  indications. 
Figure  117  represents  a  switch  lever  used  in  this  system  of 
interlocking.  Figure  1 170  shows  the  lever  in  the  normal  position. 
The  lever  is  moved  a  short  distance  horizontally  to  operate  first 
the  mechanical  locking  and  then  the  switch.  The  movement  is 
checked  in  the  reverse  indication  position,  shown  in  Fig.  1176, 


FIG.   117. — Switch  lever,  unit  type. 

until  the  indication  current  comes  in  from  the  switch  and  releases 
the  lever  for  movement  to  its  full  reverse  position. 

There  is  a  vertical  locking  system  in  the  front  of  the  machine 
very  similar  in  design  to  that  on  the  Style  A  machine.  A 
typical  arrangement  of  this  locking  is  shown  in  Fig.  118.  V  in 
Fig.  117a,  connects  with  a  tappet  in  this  locking  bed.  The  roller 
on  the  upper  end  of  V  rolls  in  a  slot  U  in  the  lever  body.  When 
the  lever  moves  from  1  to  2,  the  tappet  is  raised  one-half  of  its 
stroke  and  locks  by  means  of  the  mechanical  locking  any  levers 
that  operate  conflicting  functions.  When  the  lever  moves  from 


106 


RAILWAY  SIGNALING 


2  to  4,  the  tappet  remains  stationary,  but  the  contact  block  Z 
connected  to  the  lever  by  the  rod  W  breaks  contact  with  springs 
Y-Y  and  makes  contact  with  springs  X-X.  This  throws  the 

batteries  into  the  circuit  to 
operate  the  switch.  The 
lever  cannot  be  pulled  out 
any  farther  until  it  is  un- 
locked, the  operation  of 
which  is  explained  as 
follows: 

When  the  lever  moves 
from  1  to  2,  the  projection 
M  strikes  against  K  on 
indication  latch  L,  tilting 
the  latch  so  that  as  the 
lever  is  pulled  out  farther, 
the  projection  J  will  engage 
the  tooth  Q.  As  the  lever 
moves  from  2  to  4,  the  tooth 
Q  meshes  with  the  teeth  on 
cam  N  causing  it  to  turn 
on  its  axis.  This  rotation 
causes  dog  P  to  be  thrown 
under  the  end  of  latch  L, 
holding  the  latch  so  that 
when  the  lever  moves  to 
position  4,  the  tooth  Q 
strikes  projection  J  pre- 
venting any  further  move- 
ment until  the  switch  is 
thrown  and  indication 
given.  The  indication 
current  through  indication 
magnet  /  lifts  the  armature 
T  causing  plunger  R  to 
strike  the  dog  P  which 
turns  to  release  latch  L  and 

unlocks  the  lever  for  final  movement  from  4  to  5.  The  movement 
from  4  to  5  allows  the  tappet  to  complete  its  throw  and  unlocks 
sufficient  levers  to  complete  the  line-up.  If  the  lever  moves 
beyond  3,  it  cannot  be  advanced  beyond  4  nor  returned  beyond  2 


ELECTRIC  INTERLOCKING 


107 


unless  an  indication  is  given.  Such  an  indication  cannot  be  ob- 
tained until  the  switch  movement  is  complete,  either  entirely 
open  or  entirely  closed. 


HHilil 

Battery 


Switch  Mechanism 
Motor-  Field 


Lever  Full  Normal 

A-  AT  REST-  NO   CURRENT   FLOWING 


Switch  Normal 


Lever  at  Reverse 

Indicating  Position 

B- OPERATING 


Switch  leaving 
Normal  Position 


Lever  at  Reverse 
Indicating  Position 

C  -  INDICATING 


Switch  Reverse 


Lever  Full   Reverse  Switch  Reverse 

0  -  AT   REST  -  NO  CURRENT  FLOWING 

FIG.  119. — Simplified  circuits  for  Model  2  or  Model  4  switch  machine. 

66.  Switch  Lever  Wiring. — The  movement  of  the  switch  is 
controlled  by  three  wires — a  main  common  wire  on  which  the 
battery  is  located,  and  a  normal  and  a  reverse  control.  These 


108 


RAILWAY  SIGNALING 


control  wires  are  also  used  for  giving  indications,  the  normal  control 
for  reverse  indications  and  the  reverse  control  for  normal  indica- 


tions.    The  two  control  wires  are  connected  to  opposite  springs 
of  the  circuit  controller. 

67.  Model  2  Switch  Machine. — When  the  lever  is  moved  to 
position  4  in  Fig.  117a,  the  circuit  is  made  through  the  controller 


ELECTRIC  INTERLOCKING 


109 


contacts  and  current  flows  from  the  plus  or  operating  bus  bar 
through  the  safety  magnet  S,  Fig.  120,  through  the  indication 
selector  and  controller  contacts  and  through  the  reverse  control 
wire  to  the  switch  motor.  The  return  is  by  the  main  common. 
This  causes  the  Motor  A,  Fig.  122,  to  operate  the  switch  as 
follows:  The  armature  of  Motor  A  is  connected  by  a  series  of 
gears  to  main  gear  D\.  Pivoted  to  the  frame  is  a  cam  crank  E 
actuated  by  a  stud  on  the  main  gear  D\.  Driving  rod  G,  con- 
nected to  this  stud,  operates  a  tee  crank  H,  one  arm  of  which  is 


FIG.  121. — Model  2  switch  machine. 

connected  by  the  detector  bar  driving  link  N  to  a  straight  bar 
compensator  that  operates  the  detector  bar.  The  other  arm  of 
the  tee  crank  H  is  connected  to  the  lock  plunger  7.  In  the  newer 
installations,  however,  the  detector  bar  is  frequently  omitted 
and  the  track  circuit  substituted,  as  will  be  seen  in  a  later 
chapter. 

Fastened  to  the  lower  arm  of  the  cam  crank  E  is  rod  J  that 
shifts  the  switch  points.  B  is  a  pole  changer  that  is  operated  by 
a  rod  M  connected  with  the  pole  changer  movement  L,  after 
lock  plunger  I  has  passed  through  the  lock  rod  K.  The  lock 


110 


RAILWAY  SIGNALING 


plunger  /  also  passes  through  a  hole  in  the  flattened  portion  of  J 
giving  additional  safety. 


DETECTOR    BAR 
CONNECTION 


M  N        0 


FIG.   122. — Model  2  switch  machine. 


A    Motor 

B     Pole  Changer 

C    Friction  Clutch 

Dj  Main  Gear 

Di  Intermediate  Gear 

E    Cam  Crank 

F    Stud  on  Main  Gear 

G    Driving  Rod 


//  Lock  Crank 

I  Lock  Plunger 

J  Throw  Rod 

K  Lock  Rod 

L  Pole  Changer  Movement 

M  Pole  Changer  Connecting  Rod 

N  Detector  Bar  Driving  Link 

O  Pin 


The   main   gear   DI   makes   one    complete   revolution   while 
opening  or  closing  the  switch  points.     During  the  first  third  of 


ELECTRIC  INTERLOCKING  111 

the  revolution,  the  lock  crank  H  is  shifted,  raising  the  detector 
bar  and  pulling  the  lock  plunger  /  out,  unlocking  the  switch; 
during  the  second  third,  the  switch  is  thrown;  and  during  the 
last  third,  the  detector  bar  is  lowered,  the  switch  is  locked, 
throwing  the  pole  changer.  The  pole  changer  is  thrown  as  soon 
as  the  plunger  /  passes  through  lock  rod  K.  This  disconnects  the 
motor  from  the  reverse  control  wire  and  closes  contacts  which 
connect  the  motor  to  the  reverse  indication  wire.  The  mechan- 
ism is  so  constructed  as  to  allow  the  armature  to  continue  to 
run  for  a  short  time  due  to  the  momentum  it  had  as  a  motor. 
The  motor  then  becomes  a  generator  driving  indication  current 
from  the  positive  terminal  through  the  main  common,  polarized 
relay,  indication  magnet,  indication  selector  contact,  lever 
contact,  reverse  indication  wire  and  pole  changer  contact  back 
to  the  armature  which  is  negative  when  the  motor  is  running  as 
a  generator.  This  lifts  armature  T  and  the  plunger  R,  Fig.  1176, 
and  disengages  the  latch  L  and  allows  the  lever  to  finish  its  move- 
ment. This  is  called  dynamic  indication.  The  generator  stops 
in  a  very  short  time,  for  driving  this  current  acts  as  a  "snubber." 

The  motor  is  a  series-wound  four-pole  motor.  For  operating 
a  single  switch  the  four  field  coils  are  usually  connected  in  series, 
but  for  operating  more  than  one  set  of  switch  points,  as  movable 
frog  points,  the  coils  are  divided  into  two  sets  of  two  coils  each  in 
series,  and  the  two  sets  are  connected  in  multiple.  This  con- 
nection gives  the  machine  more  power.  The  pole  changer 
automatically  disconnects  the  motor  from  the  battery  after  a 
switch  movement  and  at  the  same  time  reverses  the  armature 
terminals  for  indication  purposes,  thus  leaving  the  motor  con- 
nections in  the  proper  position  for  the  next  operation.  The 
reversal  in  the  direction  of  rotation  of  the  motor  is  accomplished 
by  reversing  the  direction  of  current  flow  through  the  armature. 

The  contact  block  may  be  shifted  also  by  means  of  two  sets  of 
solenoid  magnets,  Fig.  123.  If  any  obstruction,  such  as  snow  or 
ice  on  the  track,  will  not  allow  the  switch  points  to  fit  snugly 
against  the  rail,  the  direction  of  the  current  through  the  motor 
may  be  reversed  by  shifting  the  lever  between  2  and  4,  reversing 
the  direction  of  the  current  through  the  solenoids;  and  the  switch 
may  then  be  thrown  in  the  opposite  direction.  If  this  movement 
back  and  forth  be  repeated  a  few  times,  the  obstruction  may 
frequently  be  removed.  There  are  fuses  on  the  control  wire 
line  of  such  size  that  in  case  a  switch  should  stick  or  the  armature 


112 


RAILWAY  SIGNALING 


could  not  rotate  for  any  reason  while  the  current  is  applied,  the 
fuses  would  melt  before  the  motor  would  burn. 

To  guard  against  a  false  indication  from  a  short-circuit  between 
control  wires  while  the  battery  current  is  flowing  through  the 
motor  to  move  the  switch,  a  safety  magnet  S,  Fig.  120,  is  mounted 
beneath  indication  magnet  /.  The  armature  T  of  magnet  / 
rests  directly  on  the  poles  of  S.  Magnet  S  is  in  the.  battery 
circuit,  and  during  the  time  the  current  is  flowing  to  the  switch 
motor,  the  armature  T  is  held  so  firmly  to  S  that  it  cannot  be 
drawn  to  I  and  a  false  indication  given. 


FIG.  123. — Pole  changer  for  Model  2  switch  machine. 

The  safety  magnet  protects  against  the  possible  receipt  of 
an  improper  indication  due  to  an  accidental  cross  between 
control  wires  during  the  time  when  the  current  is  flowing  through 
the  lever  contacts  to  operate  the  function.  From  the  time  when 
the  lever  is  moved  to  the  new  operating  position  until  the  movement 
of  the  switch  machine  is  completed,  the  indication  selector  further 
insures  against  the  possible  receipt  of  an  improper  indication. 
At  all  other  times  protection  against  improper  operation  and 
indication  is  secured  by  means  of  the  polarized  relay.  If  there 
should  be  a  foreign  current  flowing  through  the  reverse  control 
wire  when  the  switch  is  normal,  the  armature  of  the  polarized 
relay  would  operate  to  open  the  circuit  breaker  and  disconnect 
the  battery  from  the  machine.  If  the  foreign  current  should 
flow  through  the  reverse  control  wire  only  when  the  battery 


ELECTRIC  INTERLOCKING  113 

is  flowing  through  the  normal  control,  the  safety  magnet  would 
prevent  the  indication  magnet  from  operating  and  at  the  same 
time  the  polarized  relay  would  operate  to  disconnect  the  battery. 
68.  Model  4  Switch  Machine. — Figure  125  shows  two  views 
of  the  Model  4  switch  machine.  The  motor  is  connected  to  a  set 
of  intermediate  gears  that  drive  the  cam  gear  D.  On  the  upper 
side  of  D  is  a  cam  slot  that  engages  the  roller  on  the  end  of  the 
locking  bar  F.  A  link  on  the  end  of  the  locking  bar  connects 
with  a  straight  bar  compensator  that  operates  the  detector  bar. 
The  locking  dogs  H  are  so  arranged  on  the  locking  bar  F  that  when 
one  dog  has  been  withdrawn  to  unlock  rod  /,  the  other  dog  will 
not  enter  its  slot  until  the  switch  points  have  been  thrown  to 


FIG.  124. — Model  4  switch  machine. 

the  opposite  side.  A  locking  bolt  L  operated  by  the  cam  move- 
ment engages  the  throw  rod  J  and  also  locks  the  switch  in  both 
open  and  closed  positions,  giving  additional  safety  to  the  opera- 
tion. To  operate  the  pole  changer  of  the  Model  4  machine 
there  is  a  tripper  arm  N  which  engages  with  a  cam  either  on  the 
upper  or  lower  side  of  wheel  D  after  the  switch  points  have  been 
shifted  and  locked  in  position  for  traffic.  The  tripper  arm 
operates  contact  blocks  Si  and  $2,  Fig.  126.  Roller  U  engages  a 
cam  slot  on  the  locking  rod  F  and  operates  the  arm  T2  and  the 
contact  arm  V. 

69.  Model  5  Switch  Machine. — Figure  127  represents  a  plan 

and  section  of  a  Model  5  direct-current  110-volt  switch  machine 

complete   with   adjustable   lock   rod,    double-end    switch    bar, 

detector  bar  connection,   circuit  controller  and  conduit    con- 

8 


114 


RAILWAY  SIGNALING 


fe;  o     ft*  &Q 


ELECTRIC  INTERLOCKING 


115 


nection  to  trunking.     It  operates  very  much  like  the  Model  4 
machine,  but  it  is  somewhat  smaller  and  more  compact. 

70.  Semi-automatic  Signal  Control. — In  Fig.  128,  when  the 
signal  lever  is  reversed,  a  battery  circuit  is  set  up  from  the  plus 
bus  bar  through  the  reverse  controller  contact,  the  control  wire,  the 
signal  motor  operating  field  and  armature,  and  main  common. 
The  first  40  degrees  of  the  mechanism  movement  does  not  change 
the  position  of  the  signal  arm,  but  puts  under  tension  a  set  of 
coil  springs  which  are  strong  enough  to  rotate  the  motor  on  the 


FIG.  126. — Pole  changer  for  Model  4  switch  machine. 
Tripper  arm  N  shown  at  the  top  of  its  vertical  movement. 

return  movement  with  sufficient  speed  to  generate  the  current 
for  energizing  the  indication  magnet  on  the  lever.  If  the  track 
circuit  be  occupied,  the  mechanism  is  held  in  the  zero  position 
against  the  tension  of  the  springs  by  the  opening  of  contact 
BI  and  the  closing  of  contact  AI  which  connects  the  holding 
field  in  series  with  the  operating  field  and  armature  of  the  signal 
motor.  If  the  track  circuit  be  not  occupied,  the  mechanism  will 
not  stop  in  the  zero  position,  but  will  continue  its  movement, 
taking  current  through  the  track  relay  armature  contact  and 
circuit  breaker  B2,  and  bringing  the  signal  blade  to  the  proceed 
position.  Just  before  it  reaches  this  position,  contact  B2  opens 


116 


RAILWAY  SIGNALING 


ELECTRIC  INTERLOCKING 


117 


and  A2  closes,  again  cutting  the  holding  field  in  series  with  the 
operating  field,  thereby  retaining  the  signal  mechanism  and  signal 
arm  in  the  proceed  position. 
If  a  train  enters  the 
track  section  controlling 
the  signal,  the  track  relay 
becomes  deenergized  and 
its  relay  armature  drops 
breaking  the  circuit  and 
allowing  the  blade  to  re- 
turn to  the  zero  position. 
This  movement  of  the 
blade  causes  the  armature 
of  the  motor  to  run  in  the 
opposite  direction  making 
it  act  as  a  "snubber"  to 
check  the  momentum  of 
the  blade.  Circuit  breaker 
contact  AI  closes,  thereby 
retaining  the  mechanism 
in  the  zero  position  during 
such  time  as  its  lever  may 
be  reversed.  The  signal 
arm  cannot  again  be  cleared 
until  the  mechanism  is  re- 
turned to  its  —40-degree 
position.  When  the  lever 
is  restored  normal,  energy 
is  cut  off  from  the  motor, 
and  the  mechanism  is  re- 
turned to  the  —40-degree 
position  by  the  tension  of 
the  coil  springs.  Just  be- 
fore the  blade  reaches  this 
position,  contact  BI  closes, 
thereby  connecting  the 

motor  armature  and  operating  field  in  their  original  closed 
circuit,  which  includes  the  indication  magnet.  The  backward 
motion  of  the  motor  generates  enough  current  to  energize  the 
indication  magnet  and  to  allow  the  lever  to  go  to  its  normal 
position.  If  the  controlling  lever  be  placed  normal  before  a 


118 


RAILWAY  SIGNALING 


train   enters  the  track  section,  the  signal  arm  returns  to  the 
stop  position  and  the  mechanism  continues  to  run  backwards 

until  it  reaches  its  —  40- 
degree  position,  generating 
current  to  give  the  indica- 
tion as  before. 

71.  Dwarf     Signals.  - 
Some     dwarf    signals    are 
operated     by     means     of 
solenoids.     There  are  two 
sets  of   coils,  a  low-resist- 

72  T  T"  *     ance  operating  coil  and  a 

*  &     high-resistance  holding  coil. 

The  plungers  of  the  solen- 
oids are  connected  directly 
to  the  arm  of  the  signal. 
As  there  is  no  means  for 
getting  dynamic  indica- 
tions, an  indication  wire 
in  addition  to  the  control 
wire  is  necessary.  In  Fig. 
129,  as  soon  as  the  signal 
lever  is  reversed  as  far  as 
it  will  go,  the  battery  cir- 
cuit is  set  up  from  the  plus 
bus  bar  through  the  lever 
controller  contacts  in  re- 
verse position  and  through 
fi<0  &  the  polarized  relay  to  the 

c*<r 
^  c 

.515 


25 

8 


-0    91 

7° 
5i  / 


operating  coils  A- A.  This 
brings  the  signal  arm  to 
the  proceed  position.  Just 
as  the  arm  reaches  this 
postion,  circuit  breaker  C 
is  opened  causing  the  cur- 
rent to  flow  through  the 

holding  coils  B-B  in  series  with  the  operating  coils  A- A ,  retaining 
the  arm  in  that  position.  No  indication  is  given  for  this  position. 
The  coils  B-B  are  high-resistance  coils  in  order  to  reduce  the 
current  as  much  as  possible.  When  the  signal  lever  is  returned 
towards  normal  as  far  as  it  will  go,  the  battery  circuit  is  broken  to 


ELECTRIC  INTERLOCKING 


119 


the  solenoid.  The  coil  spring  which  was  placed  under  compres- 
sion when  the  signal  was  cleared  now  causes  the  arm  to  return  to 
the  horizontal  position.  Its  first  movement  closes  contact  C  and 
its  final  movement  closes  contact  D.  This  permits  battery 
current  to  flow  through  the  indication  wire  and  release  the  signal 
lever  for  final  movement  to  normal.  By  observing  Fig.  129,  it  is 
seen  that  in  its  final  normal  position,  the  indication  circuit  is 
broken  in  order  to  eliminate  a  waste  of  current.  In  Fig.  130  is  a 
sketch  of  the  Model  2  solenoid  dwarf  signal  operating  mechanism. 


FIG.  130. — Model  2  solenoid  dwarf  signal  operating  mechanism, 


A  i- A  2  Operating  Coils 
Bi-Bt   Holding  Coils 
C  Operating  Contact 

D  Indicating  Contact 

Ei-Et   Solenoid  Plungers 


Yoke 
Rack 
Pinion 
Crank 


The  two  sets  of  coilsAi-^.2and  Bi-Bz  operate  the  plungers  E\-E*. 
Motion  is  transmitted  to  the  signal  arm  by  means  of  the  yoke  F, 
rack  Gy  pinion  H,  and  crank  J.  The  contact  springs  C  and  D  are 
operated  by  a  commutator  on  the  same  shaft  as  pinion  H.  Con- 
tacts C  and  D  are  both  broken  when  the  signal  arm  is  clear.  D 
is  closed  only  when  the  arm  is  horizontal  in  order  to  give  the 
indication. 

72.  Cross  Protection. — When  all  functions  are  at  rest  they 
are  on  a  closed  circuit.  In  order  to  eliminate  the  possibility  of 
foreign  currents  operating  a  function,  one  polarized  relay  of  low 
resistance  is  placed  in  the  plant  for  each  lever  on  the  machine. 


120 


RAILWAY  SIGNALING 


It  may  be  fastened  to  the  terminal  board  on  the  back  side  of  the 
machine  or  it  may  be  mounted  on  top  of  the  machine  as  shown 
in  Fig.  131.  It  is  placed  in  the  indication  circuit  and  is  so  con- 


FIG.  131  .  —  Model  2  unit  lever  type  interlocking  machine.     Collin  wood  Interlock- 
ing Plant,  L.  S.  &  M.  S.  R'y. 

nected  that  all  currents  giving  indication  must  pass  through  the 
polarized  relay  in  such  a  direction  as  will  keep  its  contact  closed, 
while  all  unauthorized  current,  such  as  would  come  from  short- 


CIRCOIT 


110  VOLT    -=- 

BATTERY   -=. 


FUNCTION  AT  REST" 
FUNCTION  BEING  OPERATED' 

FIG.  132. — Simplified  circuit  showing  the  principles  of  the  G.  R.  S.  cross  protec- 
tion system. 

circuits  or  from  foreign  circuits,  must  flow  in  the  opposite  direc- 
tion. This  causes  the  relay  to  break  its  contact  and  shut  off  the 
current  to  the  whole  plant.  In  Fig.  132  is  a  simplified  circuit 
showing  the  principle  of  this  system  of  cross  protection.  Func- 


ELECTRIC  INTERLOCKING 


121 


tion  C  is  at  rest.  The  current  through  B  normally  flows  in  the 
direction  indicated  by  the  heavy  arrow.  If  there  should  be  a 
short-circuit,  as  at  X,  while  the  function  D  is  being  operated,  the 
current  would  travel  through  B  in  the  opposite  direction,  as 
indicated  by  the  dotted  arrow,  reverse  its  polarity  and  break 
contact  through  the  circuit  breaker  A.  This,  in  turn,  would 
release  its  armature  and  break  the  circuit  to  the  whole  plant. 
Figure  133  is  a  more  comprehensive  sketch  showing  wiring  for  a 
switch  and  signal. 


PW.I  CxAMOtf 

FIQ.  133. — Circuits  for  operating  switchboard,  interlocking  machine  and  switch 
and  signal  functions. 

73.  Alternating-current  Interlocking. — In  the  case  of  alternat- 
ing-current interlocking  the  switches  and  signals  are  operated 
directly  from  a  110- volt  circuit,  25  or  60  cycles.  The  switches 
are  operated  as  in  the  direct-current  system  and  give  a  dynamic 
indication.  The  semaphore  type  of  signals,  however,  is  not 
equipped  for  dynamic  indication.  Indication  is  given  by  energy 
through  a  contact  on  the  signal  circuit  breaker,  which  is  closed 
when  the  signal  is  in  the  stop  position.  When  the  light  type 
of  signals  is  used  with  the  alternating-current  or  direct-current 
systems,  indication  is  given  through  a  back  contact  on  the  con- 
trolling relay. 

The  use  of  alternating-current  interlocking  is  not  advisable 
unless  two  reliable  sources  of  alternating-current  power  are 
available,  and  then  its  use  is  questionable  unless  a  failure  of  the 


122  RAILWAY  SIGNALING 

source  of  signal  power  also  takes  away  the  motive  power  of  the 
cars  or  trains,  as  is  sometimes  the  case  on  electric  railways. 

74.  Illuminated  Track  Diagram. — One  of  the  features  of  a 
power  interlocking  plant  is  a  track  indicator,  which  is  a  miniature 
yard  layout,  placed  above  the  interlocking  machine  in  the  tower 
to  aid  the  towerman  in  following  the  movements  of  the  trains. 
One  such  type  of  indicator  is  the  illuminated  track  diagram  in 
which  the  tracks,  switches  and  signals  are  painted  on  a  ground 


FIG.  134. — Illuminated  diagram. 

glass  set  directly  above  the  interlocking  machine,  where  it  is 
plainly  visible  to  the  towerman.  Very  small  incandescent  lamps 
controlled  by  the  track  circuits  are  placed  along  each  track  behind 
the  glass.  Two  colors  of  lamps  are  used  alternately,  red  and 
white.  When  the  track  is  not  occupied,  the  white  light  burns 
and  when  it  is  occupied  the  red  light  burns.  This  furnishes  the 
means  for  a  signalman  to  follow  easily  the  movements  of  every 
train  through  the  yard,  even  though  he  cannot  see  the  yard  itself. 
Figure  115  shows  such  a  diagram  in  the  Chicago  Terminal  of  the 


ELECTRIC  INTERLOCKING 


123 


Chicago  and  North  Western  Railway.  A  newer  type  of  illu- 
minated diagram  is  shown  in  Fig.  134.  The  miniature  lamps 
on  the  face  of  the  diagram  are  each  connected  to  a  track  circuit. 
The  current  for  illumination  is  taken  through  the  relay  points  in 
that  section  or  through  a  repeater  relay  located  in  the  tower. 
The  lamp  may  be  normally  lighted  when  the  track  circuit  is 


FIG.   135. — Electro-mechanical  interlocking  machine. 

not  occupied,  in  which  case  the  light  goes  out  as  the  train  occupies 
that  section.  The  more  general  way  is  to  have  the  lamp  illumi- 
nated only  during  the  time  the  train  is  in  the  track  circuit. 

75.  Electro -mechanical  Interlocking  Machine. — The  electro- 
mechanical interlocking  machine  is  a  combination  of  electric  and 
mechanical  interlocking  equipment.  The  large  mechanical  levers 
operate  switches  and  derails,  while  the  electric  levers  control 
signal,  electric  locking  and  indication  circuits.  The  mechanical 


124  RAILWAY  SIGNALING 

levers  are  spaced  5  in.  apart,  while  the  electric  levers  are  spaced 
2J<2  in.  apart.  Those  electric  levers  mounted  in  the  same  vertical 
plane  as  the  mechanical  are  used  for  giving  indications  of  the 
movements  of  switches  or  derails,  and  the  others  for  controlling 
the  signal  circuits. 

The  mechanical  locking  is  the  vertical  type,  operated  in  the 
same  manner  as  in  the  electric  machine.  The  rotary  controllers 
on  the  back  of  the  machine  operate  around  a  vertical  axis.  They 
are  made  in  five  tiers  with  six  contacts  in  each,  making  thirty 
contacts  for  each  circuit  controller.  This  arrangement  of  levers 
and  locking  provides  for  detector  locking  and  for  switch  and  signal 
indications.  It  permits  a  much  smaller  plant  than  would  be 
required  if  all  the  levers  should  be  of  the  mechanical  type,  and 
allows  an  extension  of  a  plant  without  enlarging  the  tower  for  lever 
space. 

UNION  SWITCH  AND  SIGNAL  COMPANY  TYPE  "F"  SYSTEM 

76.  General. — This  system  of  electric  interlocking  differs  from 
all  other  existing  systems  of  electric  interlocking  in  that  the  actual 
power  for  operating  the  switch  and  signal  mechanisms  is  drawn 
from  a  pair  of  busses  or  mains  which  extend  throughout  the  in- 
terlocking plant  so  as  to  supply  each  function  when  required. 
In  all  other  systems  of  electric  interlocking  the  power  which 
operates  any  function  is  fed  to  that  function  over  a  separate  wire 
or  set  of  wires  from  the  interlocking  machine. 

77.  Power  Supply. — The  usual  source  of  power  supply  for  the 
Type  "F"  interlocking  plants  is  a  set  of  storage  cells,  charged 
from  local  generators  or  mercury  arc  rectifiers.     However,   a 
number  of  Type  "F"   plants  employ  alternating  current  ex- 
clusively, in  which  case  provision  is  made  for  taking  this  power 
from  any  one  of  two  or  three  different  power  lines  in  order  to 
provide  a  constant  supply  of  power  in  the  event  of  failure  of  any 
of  the  lines.     In  some  installations  devices  are  provided  to  change 
the  connections  automatically  in  case  of  failure  of  power  on  the 
line  being  used.     One  hundred  and  ten  volts  is  the  usual  potential 
employed  on  the  plant,  whether  alternating  current  or  direct 
current. 

78.  Interlocking    Machine. — This    system    is    so    similar    to 
the  electro-pneumatic  system  that  the  same  interlocking  machine, 
with  slight  modifications,  is  used.     Operating  on  a  higher  voltage, 
the  indication  magnets  for  direct  current  are  wound  to  about 


ELECTRIC  INTERLOCKING 


125 


2,000  ohms  resistance.  The  contact  arrangement  for  switch 
control  is  changed  slightly;  otherwise,  the  machine  is  just  as 
described  for  the  electro-pneumatic  system. 

79.  Power  Mains. — The  power  mains  consist  of  a  pair  of 
relatively  heavy  wires  extending  throughout  the  plant  with  taps 
at  each  switch  and  signal,  not  unlike  an  electric  light  circuit. 
These  power  mains  correspond  to  the  compressed  air  line  in  the 
electro-pneumatic  system.  They  do  not  have  to  be  heavy 
enough  to  carry  current  for  operating  all  the  functions  at  the 
same  time.  Since  the  mechanical  interlocking  feature  prevents 
the  operation  of  many  of  the  functions  at  one  time,  the  mains 


FIG.  136. — Complete    operating   and    indication    circuits   for   a   single   switch. 

need  to  be  only  heavy  enough  to  supply  current  to  those  that 
can  be  simultaneously  operated. 

At  each  switch  movement  is  a  controller  connected  to  the  com- 
bination board  on  the  interlocking  machine  by  a  pair  of  small 
electric  wires.  These  controllers  correspond  to  the  switch  valves 
in  an  electro-pneumatic  plant  and  govern  the  flow  of  current  from 
the  power  mains  to  the  switch  motors.  The  switch  circuit  con- 
troller operates  on  the  polarized  principle  and  responds  to  rever- 
sals of  polarity  in  the  control  wires  by  changing  its  contacts. 
Springs  and  bands  on  the  switch  lever  roller  in  the  interlocking 
machine  are  arranged  as  a  pole  changer.  When  the  switch  lever 
is  reversed,  the  polarity  of  the  controlling  current  is  reversed,  the 
controller  contacts  change  and  the  switch  motor  operates.  In  this 
system  the  control  wires  do  not  carry  the  current  that  actually 


126  RAILWAY  SIGNALING 

runs  the  switch  motor;  the  switch  circuit  controller  is  a  high- 
resistance  instrument  and  the  control  wires  may  be  as  small  as 
mechanical  strength  will  allow.  It  is  customary  to  use  No.  16 
copper  wire  and  to  group  them  into  cables  for  protection  against 
mechanical  injury.  This  reduces  the  amount  of  copper  necessary 
in  the  plant,  especially  where  the  switches  are  located  at  a  con- 
siderable distance  from  the  tower. 

The  switch  circuit  controller  used  with  110-volt  direct-current 
control,  shown  in  Fig.  137,  is  called  the  "  normally  deenergized" 
controller  because  it  automatically  locks  itself  in  place  and 
then  cuts  off  its  controlling  current.  It  contains  a  neutral 


FIG.  137. — Switch  circuit  controller,  direct  current,  normally  deenergized  type. 

magnet  of  two  coils,  and  a  polarized  magnet  of  three  coils.  The 
neutral  magnet  is  energized  by  a  reversal  of  the  polarity  in  the 
control  wires,  current  flowing  from  one  of  the  control  wires 
through  the  coils  to  the  power  main  of  opposite  polarity. 

When  the  neutral  armature  picks  up,  its  contacts  open  the 
switch  motor  circuit  and  close  the  circuits  to  the  polarized 
magnet.  One  coil  of  the  polarized  magnet  then  receives  current 
of  a  definite  polarity  and  from  the  power  mains;  the  other  two 
coils  of  the  polarized  magnet  receive  current  from  the  two  control 
wires.  When  the  polarity  of  these  wires  has  been  reversed,  the 


ELECTRIC  INTERLOCKING  127 

polarized  armature  reverses.  The  polarized  armature  carries 
contacts  which  change  the  circuit  for  the  neutral  magnet  from  one 
of  the  power  mains  to  the  other.  Thus  the  neutral  magnet  be- 
comes deenergized,  and  its  armature  is  released,  mechanically 
locking  the  polarized  armature  in  place.  Its  contacts  open  the 
two  circuits  to  the  polarized  magnet,  and  close  the  switch 
motor  circuits  to  throw  the  switch.  All  the  magnets  of  the 
controller  are  thus  deenergized  until  the  next  reversal  of  the 
polarity  of  the  control  wires  by  the  switch  lever. 

This  controller  also  contains  an  overload  circuit  breaker. 
Should  the  switch  points  be  obstructed,  the  switch  motor  would 
be  overloaded  and  the  breaker  would  open  as  any  circuit  breaker 
would.  It  is  so  arranged,  however,  that  it  is  reset  by  the  neutral 
armature  when  the  switch  lever  is  moved  to  the  other  indicating 
position.  Thus  the  switch  motor  is  protected  without  the  use  of 
fuses  which  require  replacement;  and  the  operator  can  move  the 
switch  back  and  forth  in  an  effort  to  dislodge  or  crush  the  obstruc- 
tion. A  separate  set  of  contacts  on  the  switch  movement 
opens  the  motor  circuit  when  the  switch  has  been  thrown  and 
locked.  Figure  136  shows  the  complete  operating  and  indication 
circuits  for  alternating  current  to  operate  a  single  switch. 

The  control  of  signals  in  the  Type  "F"  system  is  accomplished 
very  much  as  it  is  done  in  the  electro-pneumatic  system,  except 
that  an  electrical  device  must  replace  the  air  valve.  Two  small 
wires  connect  the  signal  lever  with  a  relay  or  its  equivalent  at  the 
signal.  That  relay  when  picked  up  closes  the  signal  motor  cir- 
cuit from  the  power  mains.  When  the  signal  lever  is  restored 
to  its  normal  indicating  position,  it  breaks  the  connection  to  the 
control  wires,  the  relay  drops  and  the  signal  falls  to  the  stop 
position  by  gravity. 

80.  The  Indicating  System. — The  indicating  system  is  es- 
sentially the  same  as  that  described  for  the  electro-pneumatic 
system  with  only  such  changes  as  are  necessitated  by  the  differ- 
ence in  voltage.  Obviously,  the  indicating  system  which  is 
independent  of  the  control  system  may  be  of  a  different  voltage, 
may  be  operated  from  a  different  source  of  power,  or  may 
be  alternating  current  when  the  control  system  is  direct  current. 
Each  switch  movement  embodies  a  pole-changing  indication  cir- 
cuit controller  that  controls  a  polarized  relay  in  the  tower.  Each 
signal  when  in  the  stop  position  completes  a  circuit  for  its 
indication  just  the  same  as  in  the  electro-pneumatic  system. 


128 


RAILWAY  SIGNALING 


81.  Style  "M"  Switch  Movement.— Figure  139  shows  a  Style 
"M"  switch  and  lock  movement  used  for  throwing  switches  and 
derails.  It  consists  essentially  of  motor,  clutch,  reduction  gears, 
mechanical  movement  arranged  to  operate  in  the  usual  order  to 
unlock,  throw  and  lock  a  switch,  and  circuit  controller  that  does 
the  double  duty  of  opening  the  motor  circuit  after  the  switch  is 
thrown  and  locked,  and  of  controlling  the  indication  circuit. 
The  purpose  of  the  clutch  is  to  absorb  shocks  due  to  the  momen- 
tum stored  up  in  the  rotating  armature,  and  to  limit  the  load  that 
may  be  imposed  upon  the  motor  by  an  obstructed  switch. 


FIG.   138. — Style  "M"  switch  layout. 

(B)  illustrates  the  normal  positions  of  the  immediate  parts 
instrumental  in  throwing  and  locking  the  switch  points.  Start- 
ing from  this  position  a  reverse  movement  is  begun  by  the 
clockwise  rotation  of  combined  shaft  and  crank  arm  X.  Lug 
xr  on  the  top  of  crank  X  acting  against  roller  z'  on  motion  plate 
Z,  effects  the  unlocking  of  the  switch  points.  Meanwhile,  roller 
x  on  the  underside  of  crank  X  has  moved  through  an  arc  of  40 
degrees  in  groove  y  in  switch  operating  bar  Y,  thus  freeing 
the  bar  for  the  reverse  stroke.  During  the  next  140-degree 
revolution  of  crank  X,  roller  x  engages  the  reverse  operating 
face  of  groove  y  and  throws  switch  operating  bar  7  to  the  reverse 
position. 


ELECTRIC  INTERLOCKING 


129 


(C)  shows  the  relative  mid-stroke  positions  of  the  switch 
operating  bar  Y  and  lock  bar  Z;  the  crank  X  is  still  rotating 
clock-wise;  but  is  not  transmitting  motion  to  the  lock  bar,  as 


(A)  Switch  and  lock  movement  assembled. 


(B)  Diagram  of  driving  parts  in  normal  position. 


(O  Diagram  of  driving  parts  in  middle  (D)  Diagram  of  driving  parts  in  reverse 

position.  position. 

FIG.  139. — Style  "M"  switch  and  lock  movement. 

lug  x'  has  become  disengaged  from  roller  c'  and  the  arcs  of  contact 
at  v  and  v'  between  the  crank  X  and  lock  bar  Z  are  radial  to  the 
center  of  the  crank  shaft. 

9 


130 


RAILWAY  SIGNALING 


The  complete  reverse  position  is  shown  in  (D).     Roller  x  on 
crank  X  acting  in  groove  y  has  pulled  operating  bar  Y  in  and 


M 


Style  "M"  lock  box  and  inverted  view  of  circuit  controller. 


Style  "  M  "  circuit  controller  with  point  detector. 
FIG.  140.  —  Style  "  M  "  indication  circuit  controller. 


secured  it;  lug  x2  has  come  into  contact  with  roller  z,  thus  driving 
locking  bar  Z  to  the  full  reverse  position. 


ELECTRIC  INTERLOCKING  131 

Starting  from  the  normal  position  of  the  main  crank,  which 
is  20  degrees  beyond  dead  center,  the  consecutive  events  and 
respective  angular  positions  of  the  crank  are  as  follows: 

Degrees 

0       Normal  position. 

5       Indication  supply  opened  and  relay  shunted. 

10       Normal  motor  circuit  closed. 

15       Detector  bar  even  with  top  of  rail. 

20       Dead  center. 

40       Points  unlocked. 

40 180  Degrees — Throwing  switch  points. 

200       (Dead  center)  points  locked  full  width  of  lock  bar. 
210      Reverse  motor  circuit  opened. 
215       Shunt  removed  and  indication  circuit  completed. 
220      Reverse  position. 

82.  "SS"  Control. — In  this  system,  as  in  the  electro-pneumatic 
system,  it  is  customary  to  operate  more  than  one  switch,  for 
example,  the  two  switches  of  a  crossover,  from  one  switch  lever, 
and  to  control  several  signals  governing  converging  or  diverging 
routes  from  one  signal  lever;  also  it  is  customary  to  employ  the 
"L"  position  of  a  signal  lever  for  one  signal  or  group  governing 
train  movements  in  a  corresponding  direction  on  the  track,  and 
the  "R"  position  for  train  movements  in  the  opposite  direction 
over  the  same  track.  The  ability  to  accomplish  this  multiple 
control  makes  it  possible  to  employ  a  comparatively  small 
machine  for  a  large  number  of  switches  and  signals.  Where 
several  tracks  lead  onto  a  common  track,  and  each  of  these 
tracks  has  its  own  signal,  these  signals  may  all  be  controlled  by 
one  signal  lever.  The  circuits  for  these  signals,  however,  must 
be  arranged  so  that  only  the  proper  signal  will  clear.  This  is 
known  as  the  selective  control  of  converging  signals.  In  con- 
sidering the  control  of  several  signals  from  one  lever  it  must  be 
remembered  that  each  signal  governs  a  definite  route  over 
switches  and  derails  set  a  definite  way.  Each  switch  or  crossover 
controls  a  corresponding  polarized  relay  in  the  tower,  as  previ- 
ously described.  Each  relay  must  correspond  in  the  position  of 
its  polarized  armature  with  the  controlling  lever  in  order  that 
the  indication  be  received.  Therefore,  each  switch  must  have 
been  setting  in  accordance  with  its  lever  when  the  indication 
was  received.  The  control  wire  for  a  given  signal  is  not  only 
controlled  by  its  signal  lever,  but  is  also  carried  over  neutral 
and  polar  contacts  on  the  indication  or  "SS"  relays,  and  over 


132 


RAILWAY  SIGNALING 


contacts  on  the  levers  of  all  switches  and  derails  in  the  route 
governed  by  that  signal;  and  these  contacts  are  arranged  so 
that  they  are  closed  only  when  all  the  relays  and  levers  are 
properly  set  for  movement  over  that  route.  Thus,  when  a 


FIG.  141. — Track  and  signal  layout.      Alternating  current  used  in  interlocking. 

signal  is  cleared,  a  check  is  provided  that  the  switches  are  properly 
set,  that  the  switches  correspond  with  their  levers,  and  that  no 
switch  is  manually  operated  or  even  unlocked  after  the  indication 
is  received.  The  route  to  be  properly  set  for  one  signal  must  be 

Switch  Indicating  and  signal  Control  Relays 


Mechanical  SHch  Push  Buff  on 
for  "Calling  On"armconrrol 


FIG.   142. — Signal  control  circuits  for  Fig.  141. 

wrong  for  all  others;  hence  all  the  other  signal  control  wires  must 
be  open  at  certain  lever  contacts  and  relay  contacts,  preventing 
all  other  signals  from  clearing.  This  method  of  controlling 
signal  circuits  through  switch  lever  contacts  and  relays  is  known 


ELECTRIC  INTERLOCKING  133 

as  "SS"  control.  A  sample  track  layout  and  the  corresponding 
signal  control  circuit  are  shown  on  Figs.  141  and  142.  Its 
advantages  lie  in  the  high  degree  of  safety  accomplished  and  in 
avoiding  the  interruption  of  the  signal  control  wires  at  the 
switches  with  the  possibilities  of  crosses  and  grounds.  Each 
signal  control  wire  runs  direct  from  the  tower  to  the  signal. 

83.  Auxiliary    Features. — In     connection     with     the     semi- 
automatic control  of  signals,  the  push  button,  a  device  sometimes 
used  with  the  signal  levers,  as  shown  in  Fig.  98,  should  be  mention- 
ed.    Its  purpose  is  to  close  the  circuit  for  a  calling-on  arm  when 
conditions  such  as  an  occupied  track  circuit  prevent  clearing  the 
semi-automatic   arms   of   a   signal.     After   the   signal  lever   is 
reversed,  the  button  is  pushed  in,  carrying  with  it  a  vertical  pin 
that  closes  the  contacts  below  and  engages  with  a  hole  in  the 
spring  above,  retaining  it  in  the  pushed-in  position.     When  the 
signal  lever  is  restored  to  its  normal  position,  the  lever  latch 
raises  a  cam  which,  in  turn,  raises  the  spring  out  of  engagement 
with  the  pin  and  allows  the  button  to  snap  out  into  normal 
position. 

The  interlocking  machine  is  designed  to  mount  a  row  of  lever 
lights  when  desired.  These  lights  indicate  by  being  illuminated 
or  dark,  which  switches  may  be  operated  and  which  signals  may 
be  cleared. 

84.  Union  "S-7"  and  "S-8"  Electro -mechanical  Interlocking 
Machines. —  The  Union  "S-7"  electro-mechanical  interlocking 
machine  consists  of  a  standard  Saxby  and  Farmer  mechanical 
machine  above  the  locking  bed  of  which  is  a  frame  supporting 
one  or  more  electric  lever  units,  as  shown  in  Fig.  143.     The 
electric  lever  units  are  spaced  five  inches  from  center  to  center, 
the  same  as  the  mechanical  levers;  and  the  number  of  electric 
lever  units  may  be  equal  to,  but  no  greater  than,  the  number  of 
mechanical  levers  and  spaces. 

Each  electric  lever  moves  forward  and  back  through  a  total 
angle  of  60°,  and  by  means  of  bevel  gears  rotates  a  horizontal 
shaft  which  carries  the  segment  for  the  single  lock  magnet,  and  an 
insulating  roller  with  contact  bands  very  similar  to  that  in  an 
electro-pneumatic  machine.  This  shaft  also  carries  a  crank  to 
which  is  attached  the  vertical  rod  extending  down  to  the  locking 
bed,  described  in  the  following  paragraph. 

The  mechanical  locking  between  all  of  the  levers,  mechanical 
and  electric,  is  accomplished  in  the  regular  Saxby  and  Farmer 


134 


RAILWAY  SIGNALING 


locking  bed.  Electric  levers  are  connected  to  the  locking  bed  by 
adjustable  vertical  connecting  rods  which  extend  through  the 
locking  bed  and  operate  loose  sleeve  driving  pieces.  These 
driving  pieces  rotate  on  split  journals  clamped  to  the  locking 
shafts  of  mechanical  levers,  thus  permitting  an  electric  lever  to 
drive  its  locking  bar  without  interfering  with  the  operation  of  the 
locking  shaft  which  supports  the  driving  piece.  The  driving 
pieces  are  made  in  various  lengths  so  that  a  selection  of  locking 
bars  may  be  available, 

It  will  be  noted  that  a  longitudinal  locking  bar  is  required  for 
each  electric  lever  as  well  as  for  each  mechanical  lever,  thus 
necessitating  a  wider  locking  bed  than  would  be  required  for  the 
mechanical  levers  alone. 


FIG.  143.—"  S-7  "  Elec- 
tro-mechanical interlock- 
ing machine. 


FIG.  144.— "  P-5  "  Elec- 
tro-mechanical interlock- 
ing machine. 


The  "S-8"  interlocking  machine  is  a  modification  of  the 
"S-7"  machine  and  may  have  as  many  as  three  lock  magnets  on 
each  electric  lever.  It  may  also  have  its  contact  rollers  arranged 
vertically  below  the  electric  units,  where  more  space  will  permit 
a  greater  number  of  contacts.  Either  machine  may  be  equipped 
with  quick  switch,  lever  indicator  lights,  latch  contacts,  or  stick 
push  button,  thus  incorporating  practically  all  of  the  features  of 
the  electro-pneumatic  or  Type  "F"  machines. 

The  "S-7"  and  "S-8"  machines  find  their  application  at 
mechanical  interlocking  plants  where  some  of  the  functions  are 
electric,  such  as  signals,  or  remote  switches,  or  where  it  is  desired 
to  employ  electric  detector  locking,  route  locking,  check  locking 
between  towers,  or  electric  indication  of  mechanical  switches. 


ELECTRIC  INTERLOCKING  135 

In  many  cases  the  electric  units  are  added  to  an  existing  Saxby 
and  Farmer  machine,  where  the  plant  is  being  enlarged  by  adding 
switches  and  signals;  in  such  cases  existing  mechanical  signals  can 
be  converted  to  electric,  operated  by  the  electric  levers,  thus 
making  the  former  signal  levers  available  for  switches.  The 
number  of  operated  functions  can  thus  be  materially  increased 
without  adding  to  the  length  of  the  mechanical  machine,  which 
would  not  infrequently  require  enlargement  of  the  interlocking 
tower. 

85.  Union    "P-5"    Electro -mechanical    Machine. — Another 
development    in    electro-mechanical    interlocking    machines    is 
represented  by  the  Union  "P-5"  machine,  one  of  which  is  shown 
in  Fig.  144.     This  machine  is  made  by  combining  the  frame  and 
levers  of  a  Saxby  and  Farmer  machine,  with  the  electric  levers, 
locks,  spring  combination  board,  and  locking  bed  of  a  Type  "F" 
electric  machine.     In  this  arrangement  each  mechanical  lever  is 
locked  full  normal  or  full  reverse  by  the  corresponding  electric 
lever  directly  above  it,  by  means  of  horizontal  locking  bars  and 
vertical  tappets  connected  respectively  to  the  rocker-links  of  the 
mechanical  levers  and  to  cranks  on  the  electric  levers.     In  order 
to  reverse  a  mechanical  lever,  the  electric  lever  is  first  moved  to 
the  center  position,  thus  unlocking  the  mechanical  lever,  which 
can  then  be  reversed;  finally,  the  electric  lever  is  moved  to  full 
reverse,  thus  locking  the  mechanical  lever  in  the  reversed  position. 

The  locking  of  mechanical  levers  by  electric  levers  provides  for 
detector  locking  and  electric  indication  of  mechanically  operated 
switches  the  same  as  if  the  switches  were  power  operated.  Elec- 
tric levers  are  interlocked  the  same  as  in  the  Type  "F"  machine. 
Mechanical  levers  are  not  interlocked  except  through  their 
respective  electric  levers.  The  electric  levers  are  spaced  2J-^" 
between  centers,  and  the  mechanical  levers  5";  the  intermediate 
or  alternate  electric  levers  which  do  not  come  directly  above 
mechanical  levers  are  used  for  strictly  electrical  purposes,  such  as 
the  control  of  signals. 

FEDERAL  SIGNAL  COMPANY  SYSTEM 

86.  Interlocking  Machine. — The  Federal  interlocking  machine 
is  built  with  short  levers  and  with  quadrants  and  rocker-links 
similar  to  those  in  the  Saxby  and  Farmer  mechanical  plant. 
The  machine  is  made  in  sections  of  eight  levers,  spaced  3  in. 
center  to  center.     It  has  a  horizontal  locking  bed  of  miniature 


136  RAILWAY  SIGNALING 

Style  A  type  placed  directly  behind  the  levers,  and  this  may 
be  enlarged  to  suit  requirements  in  proportion  to  the  number  of 
levers  grouped  in  a  machine  by  adding  plates  to  increase  the 
depth  of  the  locking  bed.  Figure  146  shows  a  section  of  a 
two-plate  machine.  The  latch  block  roller  travels  in  the  rocker- 
link  slot  when  the  lever  is  moved  from  the  normal  to  the  reverse 
position,  and  the  lifting  of  the  lever  latch  operates  the  rocker- 
link  just  as  previously  described  in  the  mechanical  plant. 

The  tappet  bars  are  connected  to  the  rocker-link  by  a  tappet 
link.  On  the  extreme  outer  end  of  the  tappet  is  a  driver  that 
operates  the  contact  button  shaft  of  an  auxiliary  circuit  controller. 


FIG.   145. — Federal  interlocking  machine. 

This  controller  furnishes  a  means  whereby  electric  checking  of 
the  position  of  each  lever  in  the  machine  becomes  feasible.  On 
the  front  of  the  machine  is  another  vertical  controller  connected 
by  a  rod  to  the  tail  of  the  lever.  This  controller  moves  simul- 
taneously with  the  lever  itself.  The  auxiliary  controller  in  the 
back  moves  simultaneously  with  the  lever  latch  and  hence 
becomes  a  factor  in  the  lever  locking. 

The  front  circuit  controller  is  provided  with  a  rod  having 
three  bearings.  Between  the  top  bearing  and  the  intermediate 
one  is  a  double  pole,  double  throw,  heel  and  toe  type  of  knife 
switch.  This  switch  is  operated  by  the  roller  on  the  controller 
rod  and  functions  to  make  and  break  circuits  to  the  switch  and 
signal  mechanisms.  Between  the  intermediate  bearing  and  the 


ELECTRIC  INTERLOCKIXG 


137 


bottom  one  are  located  insulated  contact  buttons  which  are 
adjustable  on  the  controller  rod  in  relation  to  the  fixed  contact 
springs,  so  that  the  contact^  may  be  timed  to  make  and  break 
with  desired  positions  of  the  controller  rod  and  thus  control 
auxiliary  circuits  as  may  be  required  by  different  conditions  of  the 
interlocking  plant.  These  contacts  are  in  general  used  for  the 
control  of  route  locking  circuits  wherever  these  may  be  employed. 


OK     DJ          DL 


FIG.   146. — Section  through  Federal  interlocking  machine. 


Each  lever  may  also  be  equipped  with  an  electric  lock  mounted 
directly  above  the  tappet  bars  and  immediately  behind  the  levers. 
These  locks  are  of  the  solenoid  type  and  are  wound  to  a  resistance 
of  8  ohms.  They  are  arranged  to  check  or  hold  the  movement  of 
the  latch  by  means  of  notching  a  plate  on  the  tappet  in  various 
portions  of  the  cycle  of  operation.  The  most  common  cuttings 
for  the  electric  lock  are  the  " normal  and  reverse"  and  the  "half 
reverse."  When  the  lock  is  cut  "normal  and  reverse,"  a  notch 
is  provided  in  the  plate  riveted  to  the  tappet  wherein  the  solenoid 


138  RAILWAY  SIGNALING 

plunger  may  drop  and  prevent  the  lifting  of  the  latch  from  the 
normal  or  reverse  position  of  the  lever  except  when  the  lock  has 
been  preliminarily  energized  and  the  solenoid  core  lifted  from 
the  notch  in  the  locking  plate  attached  to  the  tappet.  When  the 
lock  is  cut  "half  reverse,"  the  notch  is  so  situated  that  the  lever 
may  be  returned  to  its  normal  position,  but  the  latch  will  be 
prevented  from  dropping  unless  the  lock  has  been  energized  and 
the  conditions  requisite  to  the  placing  of  the  latch  normal  have 
been  fulfilled.  The  half  reverse  cutting  is  generally  found  on 
signal  levers. 

Each  lock  is  provided  with  an  auxiliary  contact  that  holds 
the  circuit  to  the  coil  open  until  it  is  desired  to  move  the  lever 
to  which  the  lock  is  attached.  This  effects  the  saving  of  elec- 
tricity inasmuch  as  the  circuits  are  closed  only  when  it  is  desired 
to  use  them.  The  levers  are  provided  either  with  or  without 
lights  as  may  be  desired.  The  light,  however,  furnishes  a 
ready  means  of  indicating  the  condition  of  the  track  over  which 
a  switch  lever  might  govern;  and  in  general,  the  light  will  when 
illuminated,  indicate  that  conditions  are  right  for  the  energiza- 
tion of  the  electric  lock. 

87.  Type  41  Switch  Machine. — The  Type  41  switch  machine  is 
adapted  for  circuits  of  100-volt  and  20-volt  potential  direct 
current  as  well  as  for  circuits  of  varying  potential  and  frequency 
when  provided  with  suitable  alternating  current  motors.  Figure 
147  shows  an  assembly  and  part  section  of  the  switch  machine. 
The  motor,  in  the  case  of  the  direct-current  operation  is  of  bipolar 
construction.  Each  field  pole  is  furnished  with  two  field  windings, 
one  for  each  direction  of  rotation.  Since  the  control  of  the  motor 
is  effected  by  means  of  three  wires,  one  for  reverse  operation  and 
the  other  for  normal  operation,  the  double  sets  of  field  coils 
furnish  a  means  of  reversing  the  direction  of  rotation  by  merely 
energizing  one  or  the  other  of  the  two  control  wires  in  combina- 
tion with  the  common  or  return  which  is  connected  to  one  of  the 
brushes.  The  other  brush  is  connected  to  a  point  common  to 
both  field  windings. 

By  means  of  a  train  of  gears  the  motor  drives  a  main  cam  gear, 
GP,  which,  in  turn,  drives  the  circuit  controller  rods  KB  and 
the  connecting  rod  FV  attached  to  the  stud  HB.  Through  the 
medium  of  this  stud  HB,  the  rotary  motion  is  changed  to  a 
reciprocating  one.  The  rod  FV  operates  the  locking  plunger  FX. 
The  escapement  cam,  pivoted  on  stud  GY,  is  provided  with  a  stud 


ELECTRIC  INTERLOCKING 


139 


HA  that  engages  operating  connections  KK  so  that  when  stud 
HA  is  rotated  around  GY,  KK  will  be  given  a  motion  transverse 
to  the  mechanism  case,  and  being  connected  to  the  switch  points 
will  move  them  from  one  position  to  the  other.  The  escapement 
cam  FT  is  provided  with  cam  surfaces  machined  to  be  concentric 
with  the  main  stud  GZ  in  the  extreme  positions  of  the  operating 
connections  KK;  therefore,  when  rotation  of  the  main  gear  OP 
takes  place,  no  movement  of  cam  FT  occurs  until  the  operating 


BV    FH  08    GW  GZ         JX  PJ 


r^',\  I    ILXC^I 

tiltiiiltl  «IW  FX  6A  L~v  ^ i"-"^j  KJ 


FIG.  147. — Type  41  switch  machine. 

stud  HB  reaches  a  position  where  it  engages  the  end  of  the  con- 
centric cam  surface  opposite  stud  HA  from  the  center  stud  GY. 
This  movement  of  HB  engages  connecting  rod  FV,  however,  put- 
ting it  in  operation  and  moving  it  towards  the  right-hand  end  of 
the  mechanism  case.  Such  movement  withdraws  lock  plunger 
FX  from  notches  cut  in  the  lock  rod  KL  and  thus  unlocks  the 
switch  points.  Continued  rotation  of  HB  around  the  center 
GZ  moves  the  escapement  cam  FT  to  a,  position  opposite  to  the 
one  shown  in  the  figure,  while  the  second  concentric  cam  surface 


140  RAILWAY  SIGNALING 

goes  to  a  position  concentric  with  the  stud  GZ.  The  operating 
connection  KK  and  the  lock  rod  KL  move  to  their  reverse  posi- 
tions from  that  shown  in  the  figure  and  another  locking  notch  in 
KL  comes  to  register  with  the  locking  plunger  FX .  Still  further 
rotation  of  stud  HB  puts  the  operating  rod  FV  in  tension  drawing 
it  forward  and  thereby  plunging  the  lock  rod  in  its  reverse  position 
from  that  shown  in  the  figure. 

After  the  lock  plunger  has  entered  through  the  lock  rod,  con- 
tinued rotation  of  the  gear  GP  causes  the  cam  surface  provided  on 
its  top  to  engage  the  roller  studs  on  the  lower  sides  of  controller 
operating  rods  KB  and  shifts  the  insulated  contact  buttons  from 
engagement  with  the  contact  springs  and  thus  disconnects  the 
motor  from  the  operating  circuits.  The  connecting  rod  FV 
stands  at  an  angle  to  the  center  line  of  the  switch  mechanism  in 
both  the  normal  and  reverse  positions.  This  change  in  angular 
position  occurs  simultaneously  and  coincident  with  the  movement 
of  the  switch  points,  thus  enabling  the  selection  of  an  indication 
contact  to  the  right  or  the  left  of  the  center  line  closed  only  when 
the  lock  plunger  advances  towards  the  motor  a  sufficient  distance 
to  insure  its  passage  through  the  proper  notch  provided  in  the 
lock  rod. 

Sixty  two  revolutions  of  the  motor  are  required  to  throw  the 
switch.  The  first  16  are  necessary  to  move  the  detector  bar 
and  unlock  the  switch.  The  next  30  throw  the  switch;  and  the 
last  16  lock  the  switch  and  throw  the  detector  bar  again.  The 
last  revolution  of  the  motor  disconnects  it  from  the  operating 
circuit. 

In  order  to  prevent  the  mechanism  from  damage  when  it  meets 
a  serious  obstruction  in  the  switch  points,  a  friction  clutch  is 
provided  in  the  transmission  between  the  motor  and  the  main 
gear.  The  rotation  of  this  clutch,  GR,  is  caused  by  the  rotation 
of  gear  GN  due  to  the  friction  of  their  engaging  surfaces. 

A  dynamic  brake  is  used  to  control  the  operation  of  the  switch 
mechanism  between  its  final  normal  and  reverse  positions  and 
also  to  control  the  application  of  the  dynamic  braking  or  regenera- 
tive circuit  required  at  the  end  of  each  switch  operation  in  order 
to  prevent  shock  or  damage  due  to  the  sudden  stopping  of  the  parts 
at  their  extreme  positions  of  operation.  This  device  is  used  also 
to  control  the  excitation  of  the  indication  transformers.  It  is  a 
compact  electro-magnet  device  comprising  two  coils  and  a  swing- 
ing armature.  The  armature  is  used  to  close  contacts  in  accord- 


ELECTRIC  INTERLOCKING 


141 


ance  with  its  attraction  to  the  right  or  left,  and  this,  in  turn,  is 
controlled  by  the  energizing  of  the  right-  or  left-hand  windings. 
88.  Switch  Machine  Control  and  Indication  Circuits. — The 
following  description  of  the  switch  machine  control  and  indica- 
tion circuits  is  taken  from  the  January,  1920,  issue  of  the  Railway 
Signal  Engineer.1 

"The  control  and  indication  of  the  switches  is  illustrated  by  the 
typical  circuit  shown  in  the  diagram.  When  a  lever  is  operated  to 
move  a  switch,  direct  current  flows  through  the  double-pole  double- 
throw  switch  actuated  by  the  movement  of  the  lever,  and  then  over 
either  the  normal  or  reverse  control  wire  (depending  on  the  position  of  the 
lever),  then  through  the  circuit  controller  in  the  switch  machine,  and  one 
of  the  coils  of  the  circuit  controller  known  as  the  'dynamic  breaker/ 
which  is  housed  in  the  switch  machine.  During  the  initial  movement 
of  the  switch  machine  and  while  the  dynamic  breaker  is  energized  there 
is  a  bi-circuit  set  up  through  which  direct  current  is  supplied  to  the 
motor  of  the  switch  machine. 


Transformer 


Thru  Of  her 

Levers 
(Common!  CH 


To  Breaker 


AC  Supply 


FIG.    148. — Typical    control    circuit    diagram    for    switch.      (Railway    Signal 

Engineer.) 

"When  the  operation  of  throwing  and  locking  up  the  switch  has  been 
completed,  alternating  current  is  transmitted  over  the  main  direct- 
current  common  wire  and  the  alternating-current  indication  common 
wire.  Each  section  of  the  plant  has  a  branch  of  these  two  common 
wires.  The  alternating  current  transmitted  over  these  two  common  wires 
is  stepped  up  to  220  volts  when  it  reaches  the  indication  transformer 
located  in  the  switch  machine.  This  secondary  current,  at  220  volts, 
is  transmitted  to  the  'safety  and  indication  magnet'  on  the  lever 
controlling  the  function,  over  the  idle  control  wire  and  the  main  direct- 
current  common,  which  releases  the  lever  so  it  may  be  placed  in  either 
the  full  normal  or  full  reverse  position,  depending  on  the  position  of  the 
function.  The  coils  on  the  dynamic  breaker  located  in  the  switch 
machine  housing  are  of  the  slow  releasing  type,  and  hold  the  controller  in 

1  Page  61.     Electric  Interlocking  at  Winchester,  Ky.,  by  F.  H.  BAGLEY. 


142 


RAILWAY  SIGNALING 


the  energized  position  for  a  sufficient  length  of  time  after  the  direct 
current  which  operated  the  mechanism  has  discontinued  to  allow  the 
alternating  indication  current  to  perform  its  function. 

"The  'safety  and  indication  magnet/  referred  to  in  the  previous 
paragraph  and  shown  in  the  illustration,  is  equipped  with  an  armature 
at  each  end  and  automatically  selects  or  attracts  either  one  or  the  other 
of  these  armatures,  depending  upon  whether  alternating  or  direct 
current  is  passing  through  the  magnet  coils.  This  is  accomplished  as 
follows: 

"With  the  alternating  current  scheme  of  indication,  the  magnetic 
lines  of  force  will  be  set  up  through  the  path  indicated  by  the  dotted 
line,  since  the  copper  ferrules  A,  B,  and  C  will  effectively  choke  the 


"/ndiccrfion 


A  ~ 

2 

V-/VA"  T^Jl  \f' 

\\ 

v    v    v    v 

t 

F. 

* 

k* 

B 

•41 

- 

SSge* 

j.  — 

\Co//s  in  Mufftp/e  Foreigner/  Levers 
Colls  in  Series  for  Switch  Levers 

FIG.   149. — The  safety  and  indication  magnet.      (Railway  Signal  Engineer.) 

magnetic  field,  set  up  by  the  alternating  current,  from  going  through 
that  part  of  the  iron  core  enclosed  by  them.  This  will  cause  armature 
G  to  be  attracted,  which  delivers  the  indication.  The  iron  path  F  is 
of  small  cross-section  and  consequently  high  reluctance,  forming  part 
of  the  magnetic  path  for  the  magnetic  flux  set  up  by  the  alternating 
current.  If  a  direct  current  is  caused  to  flow  through  the  indication 
magnet,  the  indication  mechanism  will  not  be  operated  by  this  direct 
current,  since  the  magnetic  lines  of  force  will  then  take  the  path  shown 
by  the  arrows,  because  the  copper  ferrules  at  A,  B  and  C  have  no 
choking  effect  on  the  magnetic  flux  set  up  by  a  direct  current.  The 
path  F  carries  part  of  this  magnetic  flux,  but  on  account  of  the  great 
reluctance  of  path  F  it  cannot  carry  all  of  this  flux  so  that  part  flows 
around  through  armature  D.  Armature  G  is  not  attracted,  since  the 
large  cross-section  of  E  provides  ample  path  for  the  magnetic  flux. 
Armature  D  is  attracted,  which  opens  the  circuit  energizing  the  main 
circuit  breaker  on  the  operating  switchboard,  causing  this  circuit 
breaker  to  release  and  thereby  cutting  power  from  the  section  of  the 
plant  affected. 


ELECTRIC  INTERLOCKING  143 

"It  is  evident  that  if  direct-current  energy  should  by  some  chance  be 
applied  to  the  idle  control  wire,  it  might  have  a  tendency  to  cause  the 
switch  mechanism  to  assume  an  opposite  position  to  the  control  lever. 
Since  the  idle  control  wire  forms  a  part  of  the  indication  circuit,  and 
the  safety  and  indication  magnet  is  connected  at  all  times  between  the 
idle  control  wire  and  common,  a  portion  of  any  direct-current  energy 
applied  to  the  idle  control  wire  will  flow  through  the  safety  and  indica- 
tion magnet,  attracting  the  armature  that  opens  the  cross  protection 
circuit,  and  thus  causing  the  main  circuit  breaker  in  that  section  of  the 
plant  to  open.  This  provides  an  effective  means  of  cross  protection. 


FIG.   150. — Hall  interlocking  machine. 

"This  indication  mechanism  is  applied  in  exactly  the  same  form  to 
interlocking  machines  equipped  for  alternating-current  control,  direct- 
current  indication,  by  merely  turning  the  iron  core  around.  Then 
armature  D  is  attracted  by  the  magnetic  flux  set  up  by  the  direct- 
current  indication.  Armature  G  then  becomes  the  cross  protection 
armature,  being  energized  when  the  indication  wires  are  crossed  with 
the  control  wires  carrying  alternating  current,  and  opening  the  main 
cross  protection  circuit." 

89.  Federal  Electro -mechanical  Interlocking  Machine. — A  row 
of  miniature  levers  similar  to  those  on  the  electric  machine  is 
located  above  the  mechanical  levers  and  is  provided  with  the 
same  spacing.  Mechanical  locking  between  both  sets  of  levers 
is  accomplished  in  the  vertical  locking  bed  placed  just  behind  the 


144 


RAILWAY  SIGNALING 


mechanical  levers.  Circuit  controllers  can  be  applied  to  the 
rear  of  the  machine  and  operated  by  either  the  mechanical  or 
electric  levers. 

HALL  SWITCH  AND  SIGNAL  COMPANY  SYSTEM 

90.  Interlocking  Machine. — Each  lever  is  connected  to  a  slide 
that  moves  in  a  horizontal  plane  making  and  breaking  the  circuit 


FIG.   151. — Section  through  Hall  interlocking  machine. 


by  means  of  the  controllers  attached  to  the  rear  of  the  slide.  The 
mechanical  locking  is  of  the  vertical  type  operating  in  practically 
the  same  manner  as  that  in  the  Style  A  machine.  The  levers 
are  equipped  with  latch  pins  actuated  by  the  latch  handle  to  serve 


ELECTRIC  INTERLOCKING  145 

the  purpose  of  latch  locking.  The  levers  are  also  provided  with 
stop  dogs  to  relieve  the  indication  and  safety  dogs  and  to  leave 
them  free  to  move  regardless  of  the  pressure  exerted  on  the  lever 
handle.  Electric  locks  are  located  above  the  lever  slides  with 
notches  cut  in  the  side  to  give  the  desired  lever  locking  according 
to  requirements. 

To  prevent  the  movement  of  a  switch  lever  to  full  normal  or 
reversed  position  before  a  proper  indication  is  received,  two  me- 
chanical locking  dogs  are  arranged  in  each  lever  slide.  The  dogs 
are  mechanically  forced  down  into  a  slot  in  the  bed  plate  on  which 
the  lever  slide  rests,  and  can  be  forced  out  of  the  slot  only  by  the 
action  of  the  indication  and  safety  magnet  armatures.  The  arma- 
ture of  the  safety  magnet  has  two  vertical  lugs  projecting  up  from 
the  face  of  the  armature  plate  which  engage  with  two  horizontal 
lugs  attached  to  the  lever  slide.  The  function  of  these  lugs  is  to 
lock  the  lever  in  the  full  normal,  reverse  and  operating  positions 
with  the  safety  coil  energized.  All  the  current  for  operating  the 
switch  must  pass  through  the  safety  magnet,  which  has  two  wind- 
ings, one  a  low-resistance  winding  of  0.4  ohm,  and  the  other  a 
high-resistance  winding  of  350  ohms.  The  high-resistance  wind- 
ing is  connected  in  parallel  with  a  fuse,  which  makes  the  safety 
magnet  effective  with  or  without  the  fuse  in  circuit.  To  make  a 
complete  movement  of  the  switch  lever,  it  is  obvious  that  the 
safety  magnet  armature  must  be  energized  and  then  deenergized 
in  addition  to  the  energization  of  the  alternating-current  indica- 
tion magnet. 

91.  Switch  Movement. — The  switch  is  thrown  by  an  electric 
motor  operating  through  a  train  of  gears.  It  is  provided  with  a 
normal  and  reverse  controller,  an  indication  selector,  an  indica- 
tion transformer,  lock  rod,  throw  rod  and  locking  plunger.  The 
motor  is  connected  to  the  gearing  by  a  friction  clutch  to  elimi- 
nate the  strain  that  would  arise  if  the  gears  should  be  brought 
to  a  sudden  stop.  The  controllers  are  actuated  by  a  cam  plate 
rigidly  attached  to  the  locking  plunger.  This  makes  their  action 
positive  and  becomes  dependent  upon  the  actual  locking  of  the 
switch.  The  plungers  are  staggered  in  a  horizontal  plane  so  as 
to  make  it  impossible  for  the  normal  plunger  to  enter  the  re- 
versed notch  in  the  lock  rod,  or  vice  cersa.  The  throw  rod,  itself, 
is  locked  in  both  normal  and  reverse  positions  by  a  peculiar 
arrangement  of  the  gearing,  so  that  the  switch  cannot  be  forced 
over  by  taking  off  the  lock  rod. 
io 


146  RAILWAY  SIGNALING 

The  indication  selector  is  composed  of  two  magnets,  one  in 
multiple  with  the  reverse  operating  circuit,  and  the  other  in 
multiple  with  the  normal  operating  circuit.  Each  of  these 
magnets,  when  energized,  operates  a  set  of  contacts  corresponding 
to  the  contacts  of  its  respective  locking  plunger  controller  so 
that  the  selector  contacts  and  the  locking  plunger  controlling 
contacts  must  operate  in  conjunction. 

92.  Switch  Operating  Circuits. — The  circuit  for  a  switch  con- 
sists of  a  normal  operating  wire  shown  on  the  plan  as  NO,  a 
reverse  operating  wire  shown  on  plan  as  RO,  and  a  negative 
shown  as  Neg.,  Fig.  152. 

The  operation  is  as  follows:  Operating  the  lever  latch  handle, 
closing  the  lever  latch  contact  LL  energizing  the  lever  lock 
L,  permits  the  lever  to  be  moved  to  the  reverse  operating  position, 
which  closes  contacts  7-8  and  11-12.  Current  will  now  flow 
from  110- volt  positive  bus  over  wire  20,  10-amp.  fuse,  wire  21, 
through  low  winding  SL  of  safety  magnet,  wire  22,  contacts  8-7, 
wire  23,  over  RO  wire,  to  RO  contact  on  plunger  circuit  con- 
troller, over  wire  24  through  coil  RIS  on  reverse  indication 
selector  to  negative.  This  will  energize  the  selector  and  close 
contacts  RO,  RI,  RP  and  RD.  When  these  contacts  close, 
current  will  flow  through  the  RO  contact  on  RIS  over  wire  25, 
through  fields  RF  and  motor  armature  A  to  negative.  Immedi- 
ately the  motor  starts,  the  contactors  NO,  ND,  NI  and  NS  on 
normal  plunger  circuit  controller  will  shift  to  the  right  closing 
the  NO  contact  and  opening  contacts  ND,  NI  and  NS.  When 
the  switch  has  completed  its  full  movement,  the  contactors  of  the 
reverse  plunger  circuit  controller  will  shift  to  the  left  and  open 
the  RO  contact  and  close  the  RD,  RI  and  RS  contacts.  When  the 
RD  contact  is  closed,  it  completes  a  local  dyamic  brake  circuit 
over  wires  36  and  34,  through  the  NF  winding,  through  A  to 
negative,  to  the  RD  contact  on  selector,  through  D  winding,  to 
RD  on  plunger  circuit  controller.  This  snubs  the  motor  and 
holds  the  indication  selector  magnet  closed  for  a  predetermined 
interval  of  time,  which  is  sufficient  to  allow  the  indication  magnet 
on  lever  to  operate.  When  the  dynamic  or  snubbing  current 
ceases,  the  selector  becomes  deenergized  and  automatically 
opens  its  contacts. 

93.  Signal  Operating  Circuits. — The  operation  for  a  signal  is 
as  follows:     The  lever  is  moved  to  the  full  reverse  position  (no 
reverse  indication  being  required),  closing  contacts  3-4  and  7-8; 


ELECTRIC  INTERLOCKING 


147 


I 


148  RAILWAY  SIGNALING 

current  will  then  flow  from  110- volt  positive  bus  through  coil  A 
of  cross  protection  relay  over  wire  40,  5-amp.  fuse,  wire  41, 
contact  7-8,  wire  42,  through  coil  B  of  cross  protection  relay, 
wire  43,  contact  4—3,  signal  operating  wire  to  circuit  breaker  2 
on  signal  mechanism,  through  motor  and  clutch  in  multiple  to 
negative. 

94.  Indication  Current. — The  alternating  current  for  the  signal 
indication  circuits  and  for  the  primary  of  the  switch  indication 
transformer  is  obtained   either  from   a   commercial   source  ,of 
supply  or  is  generated  at  the  plant  by  means  of  a  J^-kw.  motor- 
generator  set  opera-ted  from  the  'storage  battery  through  contacts 
on  each  lever.     As  the  motor  starting  contacts  are  closed  only 
when  the  lever  is  in  the  indication  position,  no  battery  c  urrent 
is  consumed  when  all  levers  are  in  their  full  positions.     The 
primary  of  the  indication   circuit  is  from  alternating-current 
supply  through  the  various  coils  and  transformers  returning  to 
supply  on  110- volt  negative.     The  indication  magnets  are  design- 
ed so  as  to  be  immune  to  direct  current.     The  signal  lever 
indication  magnet  is  wound  to  operate  direct  from  the  prim- 
ary main.     The  switch  lever  indication  magnet  is  wound  to 
operate  on  not  less  than  250  volts.     A  one-to-three  transformer 
that -steps  the  indication  current  up  to  330  volts  is  located  at 
each  switch  function. 

95.  Switch  Indication  Circuit. — The  normal  indication  is  re- 
ceived from  the  switch  as  follows :     The  primary  coil  P  of  indica- 
tion transformer  was  energized  through  contact  NP  of  NIS  when 
switch    movement    was  started.     When  plunger  operated  cir- 
cuit controller  contact  NI  closed,  indication  current  flowed  from 
coil  S  of  indication  transformer  over  wire  27,  contact  NI,  wire 
35,  contact  NI  on  NIS,  over  wire  24  to  contact  RO  on  plunger 
operated  circuit  controller,  over  wire  RO,  wire  23,  contact  9-10 
wire  31,  indication  magnet  I,  wire  32,  indication  bus  and  indica- 
tion main  to  coil  S  of  indication  transformer. 

96.  Signal  Indication  Circuit. — The  signal  indication  is  re- 
ceived when  the  lever  is  moved  to  the  normal  indication  position 
closing  contacts  5—6  and  9—10  and  contact  4  on  signal  mechanism. 
(Contact  4  is  closed  only  in  zero  position  of  the  signal.)     The 
current  will  then  flow  from  the  primary  main  through  contact  4 
on  signal  mechanism  over  signal  indication  wire  to  contact  9-10 
on  lever,  over  wire  45,  through  indication  magnet  /,  over  wire  44, 
wire  43,  and  through  contact  6-5  to  negative. 


CHAPTER  VIII 
DIRECT-CURRENT  TRACK  CIRCUITS 

97.  Track  Circuits. — The  direct-current  track  circuits  used  in 
power  interlocking  and  in  automatic  block  signaling  are  operated 
by  local  batteries.  A  portion  of  the  track  is  set  apart  as  a  block, 
which  has  a  low-voltage  circuit  of  its  own  traveling  through  the 
rails,  as  indicated  in  Fig.  153.  The  blocks  are  separated  by 
insulated  joints,  while  the  rails  within  the  blocks  are  all  bonded 
to  insure  the  continuity  of  the  circuit.  At  the  end  of  the  block 
is  an  electro-magnet  known  as  a  relay,  A,  that  governs  the  opera- 
tions of  the  lock  or  signal,  or  whatever  function  is  to  be  controlled. 
When  the  coils  are  energized,  the  armature,  B,  of  the  relay  picks 
up,  making  what  is  termed  front  contact.  When  they  are  de- 
energized,  the  armature  drops  away  by  gravity,  making  back  con- 

'nts. 


P 
FIG.   153. — Track  circuit  diagram. 

tact.  These  track  relays  are  usually  wound  to  a  resistance  of 
from  2  to  4  ohms.  If  it  is  any  less,  the  armature  may  not  drop 
away  when  a  train  comes  into  the  track;  if  any  more,  it  may  not 
hold  when  the  track  circuit  is  temporarily  weakened  by  rain  or 
snow,  even  though  there  be  no  train  in  the  block. 

'At  the  opposite  end  of  the  block  is  the  track  battery,  C,  for 
which  in  the  plan  indicated,  the  track  circuit  is  always  closed. 
When  there  is  no  train  in  the  block,  the  relay  is  energized,  hold- 
ing up  the  armature  which  completes  the  circuit  to  the  signal 
motor  and  to  the  mechanism  that  retains  the  arm  in  the  proceed 
position.  When  a  train  comes  into  the  block,  much  of  the  current 
flows  across  the  axles  shunting  the  relay  and  releasing  the  arma- 
ture. This  breaks  the  circuit  to  the  motor  or  holding  device,  and 
the  signal  arm  goes  to  the  stop  position  of  its  own  accord.  The 
battery  and  relay  should  be  placed  at  the  extreme  ends  of  the 
block  to  get  the  full  benefit  of  broken  rail  protection. 

149 


150  RAILWAY  SIGNALING 

The  voltage  of  the  track  circuit  varies  from  3^  to  2  volts.  It  is 
made  low  in  order  to  avoid  as  much  leakage  as  possible  from  rail 
to  rail  across  the  ballast.  It  must  not  be  too  low,  however,  or  it 
will  not  operate  the  relay  especially  during  periods  of  rain  or 
snow,  when  the  leakage  is  the  greatest.  If  the  ballast  touches 
the  rail,  the  leakage  is  considerably  .increased.  As  the  track 
currents  are  flowing  continuously  and  as  the  signal  batteries 
are  active  except  when  a  train  is  in  the  block,  some  kind  of  battery 
should  be  chosen  that  will  not  become  exhausted  quickly. 
For  this  purpose,  the  primary  batteries  most  commonly  used  in 
practice  are  the  gravity  and  the  Lelande  types.  Two  or  three 
cells  of  either  kind  are  sufficient  for  a  track  circuit.  Storage 
batteries  are  used  to  some  extent  on  account  of  the  greater  output 
per  cell.  One  such  cell  is  generally  sufficient  for  a  track  circuit. 

The  amount  of  current  to  operate  a  4-ohm  track  relay  alone  is 
less  than  ^  watt.  As  50  per  cent,  of  the  current  in  the  track 
circuit  is  lost  by  leakage  and  10  per  cent,  by  overcoming  re- 
sistance of  the  rails,  the  battery,  and  the  relay,  the  battery 
output  should  be  about  M  watt.  In  most  cases,  the  batteries 
must  be  protected  by  inserting  some  kind  of  resistance  in  series 
with  the  track  to  reduce  the  amount  of  current  flowing  when  a 
train  is  in  the  block. 

98.  Cut  Sections. — Where  the  blocks  become  too  long  for  a 
battery  to  operate  the  relay  successfully,  cut  sections  are  em- 

(a) 


(W 


If 


FIG.   154. — Cut  section  track  circuits. 

ployed.  The  block  is  divided  into  two  or  more  sections  with  a 
relay  and  track  battery  in  each.  The  battery  of  one  section  is 
connected  through  the  armature  and  front  contact  of  the  relay 
in  the  adjacent  section  so  that  when  the  relay  of  any  section  is 
deenergized  the  circuits  for  all  sections  in  the  rear  in  that  block 
are  broken.  Figure  154a  shows  a  cut  section  in  an  ordinary 


DIRECT-CURRENT  TRACK  CIRCUITS 


151 


track  circuit  and  1546  a  cut  section  in  a  polarized  track  circuit. 
The  direction  that  the  current  flows  through  the  polarized  track 
circuit  is  controlled  by  a  pole-changer  on  the  home  signal. 

99.  Fouling  Circuits. — Fouling  circuits  are  used  for  protection 
at  turnouts  or  crossings  where  there  is  a  possibility  of  a  car  stand- 
ing on  one  track  interfering  with  those  moving  on  another  track. 
For  example,  a  car  standing  too  near  the  frog  in  a  turnout  may 
endanger  the  movements  of  trains  on  the  main  line.  The  fouling 


FIG.  155. — Fouling  circuits  at  a  turnout. 

circuits  generally  extend  to  the  clearance  point  of  the  siding, 
which  is  frequently  marked  by  a  derail. 

Figure  155  shows  a  wiring  plan  for  an  insulated  switch  protected 
to  the  clearance  point  of  the  siding.  A  pair  of  wheels  standing 
at  any  point  on  the  turnout  up  to  the  clearance  post  will  give  to 
the  block  signal  a  stop  indication  just  as  if  a  train  were  oc- 
cupying the  main  track. 

Figure  156a  shows  a  wiring  diagram  for  a  crossover  between 
two  main  tracks  controlled  by  block  signals.  Figure  1566  repre- 


FIG.   156. — Fouling  protection  at  crossovers. 

sents  another  form  of  track  circuit  so  connected  through  the 
switch  controller  that  the  opening  of  the  switch  on  either  track 
will  operate  to  throw  the  approaching  signals  to  the  stop 
position  on  both  tracks. 

100.  Insulated  Rail  Joints. — In  order  to  separate  the  rails  elec- 
trically at  the  ends  of  a  block,  some  kind  of  vulcanized  fiber  is 
ordinarily  used,  placed  between  the  ends  of  the  rails,  between  the 
splice  bars  and  the  rails,  and  around  the  bolts  that  hold  the  splice 
bars  in  place.  Occasionally  on  low-speed  tracks,  wooden-block 


152 


RAILWAY  SIGNALING 


splice  bars  are  used  on  each  side  of  the  rail  instead  of  metal  bars, 
in  which  case  the  only  fiber  necessary  is  that  between  the  ends  of 
the  rails.  Figure  157  shows  some  of  the  different  types  of 
joints  commonly  found  in  practice. 

101.  Rail  Bonds  for  Track  Circuits. — As  the  construction  of  the 
rail  joint  itself  is  an  uncertain  factor  in  the  continuity  of  the 
track  circuit;  and  as  a  scale  of  rust,  which  is  a  poor  conductor 
of  electricity,  is  likely  to  form  between  the  splice  bar  and  the 
rail,  the  intermediate  rail  joints  in  the  block  are  all  bonded. 
Where  there  is  no  return  propulsion  current  to  carry,  two  No.  8 
B.W.G.  galvanized  iron  wires  are  generally  used.  One  wire  is 


FIG.  157,  PART  1. — Insulated  rail  joints. 

sufficient  to  carry  the  track  current,  but  an  additional  one  is  used 
to  provide  for  breakage  or  other  failure.  Holes  are  drilled 
through  the  web  of  the  rail  near  the  end  of  the  splice  bar,  and  the 
iron  wires  are  held  in  place  in  these  holes  by  copper-plated  steel 
channel  pins  driven  in  around  the  wire.  The  bonds  are  generally 
placed  outside  of  the  angle  bars  to  permit  an  easy  inspection  for 
broken  wires.  Where  there  is  a  propulsion  current  to  consider, 
however,  heavy  copper  bonds  are  required  at  each  joint,  adding 
a  considerable  item  of  expense. 

102.  Neutral  Relay. — The  two  coils  of  the  relay  shown  in 
section  in  Fig.  159,  are  protected  from  mechanical  injury  by 
hard  rubber  shells,  M,  or  by  insulating  varnish.  The  wires  that 
energize  the  coils  are  connected  to  the  two  binding  posts,  P. 
The  armature,  A,  is  hinged  at  the  back  of  the  poles  and  very 


DIRECT-CURRENT  TRACK  CIRCUITS  153 


Continuous. 


Weber. 


Keystone. 
FIG.   157,  PART  2. — Insulated  rail  joints. 


154 


RAILWAY  SIGNALING 


Rail  bond  for  track  circuit.    P.  &  M.  bond  protector. 

*  0.322" 


Total  Taper  £  "per  fr. 

R.  S.  A.  channel  pin,  plan  1086. 
Fia.  158. — Rail  bonds  for  track  circuits. 


PLAN  view 


INVERTED  PLAN  VIEW 
BOTTOM  PLATE  REMOVED 


SECTIONAL  SIDE  VIEW 

FIG.  159.— Neutral  relay. 


DIRECT-CURRENT  TRACK  CIRCUITS 


155 


little  movement  is'  necessary  to  make  and  break  contact.  Two 
small  non-magnetic  stops  attached  to  the  lower  end  of  the  pole 
pieces  provide  a  slight  air  gap  between  the  pole  pieces  and  the 
armature,  thereby  eliminating  the  possibility  of  the  armature's 
sticking  on  account  of  residual  magnetism  in  the  cores.  The 
contact  fingers,  K,  are  fastened  to  the  armature  by  bakelite 
studs  so  as  to  insulate  them  electrically.  The  tips  of  the  fingers 
where  they  touch  the  front  and  back  contacts  are  made  of  silver 
or  platinum.  The  circuit  for  front  contact  is  made  through  the 


FIG.   160. — Neutral  relay.     (Union  Switch  &  Signal  Co.) 

binding  post  F  and  back  contact  through  the  post  B.  One 
terminal  of  the  control  circuit  is  fastened  to  the  binding  post  G 
and  the  other  to  F  or  B  according  to  whether  front  or  back 
contact  is  required.  The  armature  and  contact  fingers  are 
enclosed  in  a  transparent  dustproof  case  to  protect  them  from 
dust  and  moisture  and  from  mechanical  injury.  While  the  wind- 
ings for  practically  all  track  relays  vary  from  2  to  4  ohms,  the 
resistance  for  line  relays  runs  much  higher,  even  up  to  1,000  ohms. 

A  comparison  of  the  2-  and  4-ohm  relays  printed  in  the  Pro- 
ceedings of  the  Railway  Signal  Association  presents  the  following 
points  for  consideration:1 

1  Page  5,  1918. 


156  RAILWAY  SIGNALING 

1.  Because  of  its  lower  operating  voltage,  the  2-ohm  relay  will  operate 
with  a  lower  ballast  resistance. 

2.  The  2-ohm  relay  is  less  susceptable  to  leakage  current  from  adjacent 
battery  entering  track  circuit  through  insulated  joints. 

3.  The  energy  consumption  for  the  2-ohm  relay  on  equal  track  circuits  is 
approximately  50  per  cent,  less  when  the  track  is  occupied.     When  the 
track  is  not  occupied  the  energy  consumption  will  be  less  when  the  ballast 
resistance  is  less  than  5  ohms  per  1,000  ft. 

4.  The  length  of  track  circuit  may  be  increased  with  the  use  of  the  2-ohm 
relay  if  no  foreign  current  is  present  and  the  resistance  between  the  battery 
and  track  is  not  less  than  the  recommended  limiting  resistance. 

5.  On  track  circuits  of  equal  length  the  2-ohm  relay  gives  equally  as 
good  protection  against  broken  rails  where  no  foreign  current  is  present. 

6.  On  track  circuits  of  equal  length,  the  2-ohm  relay  will  release  with  a 
higher  shunting  resistance  across  .the  rails  when  foreign  current  entering 
the  track  circuit  is  less  than  350  amp. 

7.  Considering  track  circuits  of  equal  length  and  with  other  conditions 
equal,  no  definite  recommendations  can  be  made  in  favor  of  either  the  2-ohm 
or  the  4-ohm  relay  where  foreign  current  is  present,  on  account  of  there 
being  conditions  where  each  has  its  advantages  over  the  other. 

8.  With  a  foreign  current  present,  the  2-ohm  relay  on  a  track  circuit  of  its 
maximum  operable  length  will  receive  more  combined  foreign  and  track 
battery  current  than  will  be  received  by  a  4-ohm  relay  on  a  track  circuit  of 
its  maximum  operable  length. 

9.  When  a  battery  lead  or  a  rail  is  broken  and  the  track  circuit  between 
the  break  and  the  relay  is  shunted,  the  2-ohm  relay  will  be  more  susceptible 
to  foreign  current  than  the  4-ohm  relay.     With  the  track  circuit  not  shunted, 
the  2-ohm  relay  will  be  more  readily  picked  up  by  foreign  current  only 
when  that  current  enters  the  track  circuit  through  a  resistance  less  than 
5  ohms. 

In  view  of  the  above  statements,  your  Committee  recommends  the  use  of 
the  2-ohm  relay  with  caustic  soda  battery,  provided  the  recommended 
limiting  resistance  is  used  in  series  with  the  battery.  The  recommended 
limiting  resistance  should  also  be  used  in  series  with  the  battery  wherever 
the  4-ohm  relay  is  used  with  caustic  soda  battery. 

103.  Polarized  Relays. — In  addition  to  the  two  coils  found  in 
the  neutral  relay,  there  is  a  steel  bar,  P,  that  is  permanently 
magnetized  in  the  polarized  relay,  Fig.  161.  The  polarized 
armature,  PA,  rotates  in  a  horizontal  plane  about  a  vertical 
axis  through  X.  The  armature  is  supported  between  the  lower 
end  of  P  and  the  bracket  S.  The  top  of  the  permanent  magnet 
is  generally  the  north  pole  and  the  bottom  the  south  pole.  The 
entire  polarized  armature  then  becomes  a  south  pole  by  induction. 
The  polarized  armature  can  operate  only  when  the  neutral  relay 
is  energized,  at  which  time  one  of  the  pole  pieces  of  the  coils 
becomes  a  north  pole  and  one  a  south  pole.  The  north  pole 


DIRECT-CURRENT  TRACK  CIRCUITS 


157 


will  attract  the  polarized  armature  while  the  south  pole  will 
repel  it,  causing  a  slight  rotation.  The  fingers,  K,  connected  to 
the  armature  by  insulators,  make  contact  connections  with  the 
binding  posts  B. 


PLAN  VIEW 


INVERTED  PLAN  VIEW 
BOTTOM  PLATE  REMOVED 


FRONT  VIEW 
GLASS  SECTIONED 


SECTONAL  SIDE  VIEW 

FIG.  161. — Polarized  relay. 

104.  Track  and  Signal  Batteries.— The  electrolyte  of  the 
gravity  cell  is  made  up  of  two  liquids  that  separate  themselves 
by  gravity.  A  saturated  solution  of  copper  sulphate  is  used 
in  the  lower  half  of  the  jar  and  a  dilute  solution  of  zinc  sulphate 
in  the  upper  half.  The  copper  element  rests  on  the  bottom  of 
the  jar  in  the  copper  sulphate  solution  and  the  zinc  clement  is 
supported  at  the  top  in  the  zinc  sulphate  solution.  The  gravity 
cell  finds  its  best  service  where  the  current  demand  is  practically 
continuous  as  it  is  in  the  case  of  the  track  circuit.  Where  the 
current  is  broken  for  some  time  a  chemical  change  takes  place 
that  practically  destroys  the  efficiency  of  the  cell.  As  the  cell 


158 


RAILWAY  SIGNALING 


must  be  renewed  about  once  a  month,  it  involves  considerable 
expense  for  maintenance.  The  internal  resistance  of  the  cell  is 
very  high. 


PORCELAIN  COVER 


IS5UE:I9II 


PORCELAIN  JAR 


NOTES. 

COMPLETE  CELL.  A  complete  cell  consists  of  * 
jar,  cover  and  renewal  with  one  hexagon  nut,  two 
wing  nuts  and  two  washers  as  shown. 

RENEWAL.  A  renewal  consists  of  a  sealed  can  of 
caustic  soda,  sealed  bottle  of  mineral  oil  and  the  as- 
sembled elements  with  connecting  wire  and  rigidly 
connected  suspension  bolt.  Nuts  and  washers  shall 
be  furnished  with  renewals  only  when  specified. 

The  elements  shall  be  so  assembled  thct  when  at- 
tached to  the  cover  and  the  nut  on  the  upper  side 
tightened  to  place,  the  elements  will  be  at  the 
height  in  the  solution. 

Connection  to  zinc  shall  be  No.  12  B  &  S  gauge  solid 
soft  drawn  copper  wire  covered  with  an  insulation 
suitable  to  withstand  the  action  of  the  oil  and  elec- 
trolyte. Insulation  on  end  of  wire  shall  be  trimmed 

must  not  be  scored. 


proper 


nd 


copper  plated. 
over  shall  con 


CAUSTIC  SODA  SIGNAL  CELL 

(400  AMPERE  HOURS) 

R.  S.  A. 


Suspension  bolt  shall  be 
JAR  AND  COVER.     Jar 

slight  irregularities  in  manufacture.  Top  of  ja 
shall  be  square  with  vertical  axis  and  cover  shall  be 
perfectly  flat.  Manufacturer's  name  or  trade  mark 
may  be  shown  on  cover.  Porcelain  jars  shall  be  glazed 
inside  and  out  and  covers  on  top  and  edge. 

A  solution  line  consisting  of  a  slight  ridge  or  depres- 
sion extending  around  the  inside  of  porcelain  jars 
and  the  outside  of  glass  jars  shall  be  placed  as  shown 

For  heat  resisting  jars,  glass  shall  be  three-sixteenths 
inch  i3/16"l  thick  and  inside  dimensions  shall  be  as 
shown  with  reasonable  allowance  for  slight  irregulari- 
ties in  manufacture. 


1053 


FIG.  162. — R.  S.  A.  standard  caustic  soda  signal  cell. 

The  Lelande  type  covers  a  number  of  patented  cells,  among 
which  are  the  Edison,  Columbia,  Waterbury,  and  Gordon, 
varying  only  in  the  method  of  construction.  The  electrolyte 


DIRECT-CURRENT  TRACK  CIRCUITS 


159 


is  a  strong  solution  of  caustic  soda,  while  the  elements  used  are 
zinc  and  copper  oxide.  The  cells  do  not 
deteriorate  when  not  in  service  and  may  be 
used  on  either  open  or  closed  circuits.  As  the 
total  output  of  the  cell  is  practically  constant, 
a  heavy  current  may  be  drawn  for  a  short  time 
or  a  low  current  for  a  long  time.  As  used  in 
ordinary  signal  practice,  the  cell  must  be 
renewed  about  every  eight  or  nine  months. 
The  internal  resistance  of  the  cell  is  so  low 
as  to  require  some  kind  of  resistance  in  series 
with  the  battery  to  prevent  it  from  becom- 
ing exhausted  too  quickly  when  used  on  track 
circuits. 


FIG.  163.— Edison 
primary  cell. 


FIG.  164.— Waterbury  signal  cell. 

The  storage  cell  is  formed  of  two  lead  plates  with  an  electro- 
lyte of  dilute  sulphuric  acid.     The  plates  of  themselves  will  not 


160 


RAILWAY  SIGNALING 


FIG. 165  — 
Columbia  signal 
cell. 


form  a  current  as  the  primary  batteries  do,  but  must  be  charged 
by  the  current  from  a  generator  or  from  a  mercury  rectifier. 
Once  so  charged,  they  will  give  out  current,  but  they  must  be 
recharged  rather  frequently.  They  possess  the  advantage,  how- 
ever, of  having  a  higher  voltage,  each  cell  having  an  electro- 
motive force  of  2  volts. 

105.  Battery  Wells  and  Battery  Chutes.— 
The  batteries  used  to  operate  the  signals  are 
generally  housed  in  battery  wells,  located  near 
the  base  of  signals.  Most  of  these  wells  are  now 
made  of  concrete,  as  illustrated  by  Fig.  166. 
They  are  built  in  a  material  yard,  and  shipped  to 
the  place  where  they  are  to  be  used.  Some  are 
set  into  the  ground  to  within  a  foot  of  the  top, 
while  others  are  set  with  their  tops  flush  with  the 
surface  of  the  gfound.  This  not  only  provides  a 
safe  place  where  the  batteries  will  not  be  dis- 
turbed, but  also  protects  them  against  freezing 
temperatures.  The  well  is  usually  4  or  5  ft.  in 
diameter  and  from  4  to  8  ft.  in  depth  over  all. 
Tiers  of  wooden  shelves  are  provided  around  the  wall  of  the 
well  to  support  the  battery  cells. 

The  two  or  three  cells  required  for  the  track  battery  when 
housed  alone  are  generally  placed  in  a  battery  chute,  the  greater 
portion  of  which  extends  below  the  ground.  The  chutes  are 
usually  made  of  cast  iron,  just  large  enough  in  diameter  to  con- 
tain the  cells  when  they  are  supported  one  above  another.  The 
length  of  the  chute  varies  from  5  to  7  ft.;  but  even  longer  ones 
are  used  where  the  temperature  gets  low  enough  to  require  the 
cells  to  be  placed  at  greater  depths  to  prevent  freezing  or 
to  maintain  the  proper  efficiency.  About  a  foot  of  the  chute 
remains  above  the  ground;  and  some  proper  construction 
is  utilized  to  so  connect  it  with  the  trunking  that  the  wires 
will  not  be  exposed  to  the  weather.  In  order  that  they 
may  be  easily  removed  for  repairs  or  renewals,  the  battery 
cells  are  supported  in  wooden  elevators  raised  and  lowered  by 
a  rope. 

106.  Cable  and  Relay  Posts. — Cable  posts  are  used  to  house 
and  support  wires  where  connections  are  made  between  lines 
and  relays.  At  points  where  it  becomes  necessary  to  install  a 
relay  in  its  own  housing,  the  relay  box  is  generally  attached  to 


DIRECT-CURRENT  TRACK  CIRCUITS 


161 


the  cable  post,  as  shown  in  Fig.  167.     Figure  168  represents  a 
battery  chute  with  a  relay  box  attached. 

107.  Trunking. — The  trunking  used  to  carry  the  wires  from  the 
track  connections  to  the  battery  wells  and  battery  chutes,  to 
the  track  relays  and  the  signal  towers,  is  generally  made  of  wood, 
frequently  treated  with  some  chemical  agent  to  protect  it  against 


FIG.   166. — Massey  80-cell  battery  well. 

decay.  As  shown  in  Fig.  169,  it  may  be  either  grooved  or  built- 
up  depending  upon  the  size  of  the  opening  required.  The  trunk- 
ing is  buried  flush  with  the  surf  ace  of  .the  ballast  when  used  within 
the  roadbed,  and  is  supported  on  substantial  taskes  when  carried 
along  the  ground.  Conduits  of  fiber  and  other  materials  are 
sometimes  used,  but  they  are  laid  underground  and  are  generally 
n 


162 


RAILWAY  SIGNALING 


encased  in  concrete.  Reinforced  concrete  makes  a  practical 
trunking  where  it  becomes  desirable  to  install  a  more  permanent 
type. 

108.  Insulated  Head,  Front,  and  Tie  Rods. — In  order  to  main- 
tain the  track  circuit  intact  through  the  turnout,  all  connections 
between  the  two  rails,  such  as  head,  front,  and  tie  rods,  and 
the  head  plate  where  it  is  used,  must  be  insulated.  The  common 
method  of  doing  this  is  to  make  these  rods  and  plates  in  two 


FIG.  167. — Cable  and  relay  post, 
indicators. 


Switch 


FIG. 


168. — Battery  chute 
and  relay  box. 


pieces  and  bolt  them  together  with  a  fiber  insulator  between,  as 
shown  in  Fig.  171. 

109.  Lightning  Arresters. — -In  order  to  protect  the  relays  and 
other  equipment  in  track  and  signal  circuits  against  damage  by 
lightning,  two  different  appliances  have  been  devised  to  insert 
in  the  circuit — the  spark  gap  arrester  and  the  choke  coil.  One 
type  of  spark  gap  arrester  frequently  used  is  made  of  five  brass 
plates  arranged  as  shown  in  Fig.  172,  with  a  short  air  gap  between 


DIRECT-CURRENT  TRACK  CIRCUITS 


163 


FIG.  169. — Trunking  and  capping. 


FIG.  170. — Reinforced  concrete  trunking  on  New  York  Central  R.  R.  at  Utica, 

N.  Y. 


FIG.  171. — Insulated  switch  rod. 


164 


RAILWAY  SIGNALING 


FIG.   172. — Hall  lightning  arrester. 


FIG.  173. — Lightning  arresters  in  relay  box. 


DIRECT-CURRENT  TRACK  CIRCUITS 


165 


them.  The  center  plate  is  grounded;  the  other  four  are  connected 
to  the  track  and  other  circuits.  As  the  lightning  has  a  high 
voltage,  it  will  tend  to  jump  the  gap  rather  than  follow  the  wires, 
and  the  notches  on  the  edges  of  the  plates  will  aid  the  discharge, 


FIG.   174. — Hall  choke  coil  lightning  arrester. 

The  choke  coil  is  generally  made  by  winding  a  bare  copper 
wire  into  a  coil  around  a  procelain  core.  The  direct  current  of 
the  track  or  signal  circuit  will  meet  with  practically  no  resistance 
in  the  coil;  but  the  lightning,  being  a  high-frequency  alternating 
current,  will  meet  with  an  impedance  due  to  the  self  induction  of 
the  coil. 


CHAPTER  IX 
ELECTRIC  LOCKING 

110.  Wiring  Diagrams  for  Electric  Locks. — Figure  175  is  the 
Union  method  of  wiring  for  operating  a  power  distant  signal  in  a 
mechanical  interlocking  plant.  When  the  home  signal,  2,  is 
cleared,  its  circuit  breaker,  C,  is  closed  so  that  when  lever  1  is 
reversed,  the  circuit  is  complete  to  relay  D  picking  up  its  arma- 
ture and  closing  the  local  battery  circuit  to  clear  distant  signal  1 . 


.1 


J 


FIG.  175. — Wiring  for  power  distant  signal. 

The  signal  will  remain  cleared  until  lever  1  is  returned  to  its 
normal  position. 

Figure  176  is  an  indication  wiring  so  arranged  as  to  make  cer- 
tain that  the  distant  signal  is  returned  to  its  full  normal  position 
before  the  lever  latch  can  be  released.  When  lever  1  is  reversed 
after  signal  2  is  cleared,  the  distant  blade  will  go  to  clear.  Levers 


1 


FIG.  176. — Wiring  for  electric  lock. 

1  and  2  may  be  returned  to  their  normal  positions,  but  the  latch 
on  lever  2  will  not  be  released  until  the  distant  blade  goes  to  its 
full  normal  position  closing  circuit  breaker  F,  thereby  energizing 
lock  A  on  lever  2  and  unlocking  its  segment  2.  The  latch  will 
then  be  dropped  into  its  full  normal  position.  If  F  is  not  closed 
however,  A  will  not  be  energized  and  the  latch  will  remain  locked. 

166 


ELECTRIC  LOCKING 


167 


Figure  177  shows  a  form  of  an  electric  lock  to  control  the  lever 
latch  on  a  Saxby  and  Farmer  machine.     In  Fig.  178  an  arm 


FIG.   177.— Electric  lock. 


FIG.  178. — Electric  lock. 


fastened  to  the  locking  shaft  D  operated  by  the  latch,  is  connected 
by  means  of  link  F  to  a  segment  A  that  rotates  about  its  center  C. 


168 


RAILWAY  SIGNALING 


The  edge  of  this  disc  engages  a  bar,  B,  controlled  by  the  electro- 
magnet. When  this  lock  magnet  becomes  energized,  the  bar,  B, 
is  raised  clear  of  the  notch  allowing  the  locking  shaft  to  be  turned 
and  the  latch  to  be  seated  in  its  normal  position. 

Figure  179  shows  a  lock  applied  to  a  Saxby  and  Farmer 
machine.  It  is  connected  by  a  rod  directly  to  the  rocker-link 
manipulated  by  the  lever  latch.  When  the  magnet  becomes 
energized,  its  armature  lifts  the  dog  from  the  segment  notch 


FIG.  179. — Electric  lock  applied  to  a  mechanical  interlocking  machine. 

allowing  the  rocker-link  to  be  moved  by  the  lever  latch.     Figure 
180  shows  enlarged  views  of  the  lock. 

Figure  181  is  an  arrangement  by  which  the  distant  signal  is 
controlled  through  the  home  signal  and  a  section  of  bonded  track, 
or  a  track  circuit  section.  When  the  home  signal,  2,  is  cleared, 
the  circuit  breaker  A  completes  the  circuit  through  the  track 
battery  C,  energizing  the  track  relay  E,  thereby  completing  the 
local  battery  circuit  through  signal  F  causing  it  to  go  to  the  clear 
position.  As  soon  as  a  train  enters  the  controlling  track  section, 


ELECTRIC  LOCKING 


169 


relay  E  is  deenergized  causing  the  signal  F  to  go  to  the  caution 
position.  When  signal  2  returns  to  the  normal  position,  circuit 
breaker  A  opens  the  circuit  that  controls  the  relay  E,  and  signal 
F  will  continue  in  the  normal  position.  Signal  F,  brought  to  the 
clear  position  by  power  controlled  by  the  towerman  in  the  inter- 


END  VIEW  COVER  SECTIONED 


SIDE  VIEW  COVER  SECTIONED 

FIG.   180. — Details  of  electric  lock. 


locking  plant,  but  returned  to  its  normal  position  by  the  presence 
of  a  train  in  its  track  section,  is  called  a  semi-automatic  signal. 
Figure  182  is  an  elaboration  of  the  wiring  arrangement  shown 
in  Fig.  181  whereby  the  lever  to  home  signal  2  may  be  locked  in 
the  half  reversed  position.  D  is  a  circuit  breaker  on  the  drum  of 


•BE! 


FIG.   181. — Distant  signal  controlled  by  track  circuit. 

the  electric  lock  that  is  closed  when  lever  2  is  returned  to  its 
normal  position;  but  A  will  not  become  energized  until  the  distant 
signal  has  gone  to  the  full  caution  position,  closing  the  circuit 
breaker  J.  As  soon  as  A  becomes  energized,  the  latch  is  un- 
locked and  may  be  placed  in  its  normal  position. 


170 


RAILWAY  SIGNALING 


Figure  183  is  an  arrangement  whereby  the  distant  signal  and 
the  tower  indicator  B  are  controlled  by  a  short  track  section 
known  as  a  "  setting  section. "  The  section  may  be  made  as  long 
as  desired,  but  a  few  rail  lengths  will  answer  the  purpose.  When 


1 

i 

H~ 

I 

i 

^"t 

H  c 

r  i  ! 

• 

E 

J* 

f 

E  f 

FIG.  182. — Electric  lock  applied  to  Fig.  181. 

the  home  signal  E  is  cleared,  circuit  breaker  D  is  closed.  If  after 
lever  A  is  reversed,  the  armature  is  lifted  to  close  the  front  contact 
of  relay  B,  B  will  become  energized  by  battery  C  provided  there 
is  no  train  on  the  track  section  between  the  two  sets  of  insulated 


FIG.  183. — Distant  signal  controlled  by  setting  section. 

rail  joints,  and  the  armature  of  B  will  stick.  As  soon  as  F  be- 
comes energized  by  battery  C,  the  distant  signal  goes  to  clear. 
Should  a  train  come  into  the  block,  the  signal  would  return 
to  caution  and  would  remain  in  that  position  after  the 


If 


— HI|I|K 


J 


FIG.  184. — Setting  section  and  electric  lock. 

train  goes  through.  As  soon  as  /  becomes  deenergized,  B 
becomes  deenergized  and  its  indicator  goes  to  the  stop  posi- 
tion, opening  the  circuit  until  restored  by  hand. 


ELECTRIC  LOCKING  171 

Figure  184  is  an  elaboration  of  the  wiring  arrangement  shown 
in  Fig.  183  and  provides  for  a  separate  lever  to  operate  the  distant 
signal  in  connection  with  the  track  section  and  an  electric  lock  D 
to  insure  that  the  distant  signal  blade  returns  to  its  full  normal 
position.  Levers  1  and  2  may  be  returned  to  normal,  but  2  will 
remain  locked  in  the  half  reversed  position  until  circuit  breaker 
J  is  closed. 

111.  Section  Locking. — As  defined  by  the  Railway  Signal 
Association,  section  locking  is:  " Electric  locking  effective  while 
a  train  occupies  a  given  section  of  a  route  and  adapted  to  prevent 
manipulation  of  levers  that  would  endanger  the  train  while  it  is 
within  that  section." 

The  introduction  of  heavy  track  rails  has  rendered  more  or  less 
uncertain  the  effectiveness  of  the  detector  bar  in  preventing  the 


FIG.   185. — Section  locking. 

signalman  from  throwing  a  derail  or  switch  under  a  train.  With 
the  wide  rail,  there  is  a  possibility  that  the  detector  bar  would 
miss  the  tread  of  the  wheel  entirely  if  an  attempt  should  be  made 
to  throw  the  switch  under  a  train,  and  thus  it  would  fail  to  per- 
form the  only  function  it  had  to  serve.  Furthermore,  the  clips 
sometimes  fail  either  from  continual  wear  or  from  the  force  of 
the  drive  by  power  equipment. 

As  a  measure  of  greater  safety,  section,  or  detector  locking,  is 
used  sometimes  instead  of  the  detector  bar  and  sometimes  in 
addition  to  it.  It  becomes  effective  by  having  electric  locks 
attached  to  the  facing  point  locks  or  to  the  switch  levers  and 
controlled  by  the  track  relays.  The  track  section  used  for  this 
purpose  may  vary  from  100  to  300  ft.  in  length.  Figure  185 
shows  circuits  for  section  locking. 

As  the  lock  is  controlled  by  the  track  relay,  the  lever  to  which 
the  lock  is  attached  is  locked  positively  in  both  the  normal  and 
reverse  positions  as  long  as  the  track  section  is  occupied  by  a 
train.  On  certain  occasions  while  a  train  is  standing  in  a  portion 


172 


RAILWAY  SIGNALING 


FIG.  186. — Electrical    screw    hand    release.     (General    Railway    Signal    Co.) 


ELECTRIC  LOCKING 


173 


of  this  section,  it  might  become  desirable  to  energize  the  electric 
lock  in  order  to  change  the  route.  To  accomplish  this,  a  screw 
release  is  inserted  to  energize  the  lock  magnet  independently  of 
the  track  section.  A  floor  push  is  installed  in  the  locking  circuit 
as  a  matter  of  economy  in  current  consumption. 

112.  Screw  Release. — A  screw  release  is  a  device  for  mechani- 
cally releasing  the  electric  lock  on  a  lever  in  a  mechanical 
interlocking  plant  in  order  to  restore  the  levers  to  their  normal 
position  with  or  without  the  section  having  been  occupied  by  a 
train,  depending  upon  the  particular  case  in  hand.  It  intention- 
ally involves  an  element  of  time  either  to  prevent  hasty  action  on 


FIG.  187. — Clock-work  time  release. 

part  of  the  towerman  in  some  cases  or  to  penalize  him  for  negli- 
gence in  other  cases. 

An  electrical  screw  hand  release  is  shown  in  Fig.  186.  In 
its  normal  position,  the  contact  block  is  as  far  to  the  upper  end  of 
the  screw  as  it  is  possible  to  go.  To  manipulate  the  electric 
lock,  the  contact  must  move  the  full  length  of  the  screw,  requiring 
from  one  to  two  minutes  of  time  for  the  operation.  It  is  known 
also  as  a  hand  release,  time  release,  and  slow  release. 

113.  Clock-work  Time  Release. — The  clock-work  time  re- 
lease, shown  in  Fig.  187,  serves  the  same  purpose  as  the  hand 
release,  but  requires  very  little  of  the  signalman's  time  for  actual 
manipulation.  To  apply  the  release,  he  turns  the  knob  as  far  to 


174  RAILWAY  SIGNALING 

the  right  as  it  will  go.  This  winds  up  a  mechanism  of  clock-work, 
which  when  released  slowly  unwinds,  returning  the  pointer  to  its 
stop  position.  The  time  interval  is  usually  from  one  to  two  min- 
utes, but  may  be  as  much  as  four.  When  there  are  many  move- 
ments of  trains,  however,  the  interval  must  be  comparatively 
short. 

114.  Approach  Locking. — As  denned  by  the  Railway  Signal 
Association,  it  is:  " Electric  locking  effective  while  a  train  is 
approaching  a  signal  that  has  been  set  for  it  to  proceed 
and  adapted  to  prevent  manipulation  of  levers  or  devices  that 
would  endanger  that  train. " 

Approach  locking  is  an  arrangement  whereby,  after  a  train  has 
passed  a  certain  point  or  entered  a  certain  route  approaching  an 
interlocking  plant,  the  route  cannot  be  changed  after  the  signals 
have  been  accepted.  It  is  used  essentially  at  high-speed  points 
for  a  greater  protection  than  the  ordinary  crossing  signals  give. 
In  this  connection,  there  is  usually  a  preliminary  track  section 
outside  of  the  section  governing  the  distant  signal.  When  the 
train  enters  this  preliminary  section  and  the  home  signal  has 
been  cleared  the  route  cannot  be  changed  except  by  the  hand 
release.  As  soon  as  the  train  has  passed  the  home  signal,  the 
locking  is  released.  Some  type  of  indicator  controlled  by  the 
preliminary  section  or  by  the  entire  route  is  generally  used  in 
connection  with  approach  locking. 

Figure  188  is  the  Union  arrangement  for  approach  locking  used 
in  connection  with  the  lever  controlled  power  distant  signal. 
After  signal  2  is  cleared  and  its  circuit  breaker  is  closed,  lever  1 
may  be  reversed  placing  distant  signal  1  in  the  clear  position. 
When  a  train  enters  the  preliminary  section  Y-Z,  it  deenergizes 
the  lock  magnet  B.  Levers  1  and  2  can  be  returned  to  the  full 
normal  position,  but  the  latch  on  lever  2  will  be  locked  half  re- 
versed until  the  train  passes  X.  When  both  track  sections  are 
cleared,  the  lock  B  becomes  energized,  unlocks  the  latch  and  allows 
it  to  be  seated  in  its  full  normal  position. 

It  sometimes  becomes  desirable  to  change  the  line-up  of  the  sig- 
nals after  a  train  has  stopped  between  X  and  Z  in  Fig.  188.  To  do 
this,  a  screw  release  or  time  lock  is  provided.  Figure  189  shows  a 
hand  release,  also  an  approach  indicator  added  to  the  arrange- 
ment in  Fig.  188.  When  the  train  occupies  the  track  between  X 
and  Z  in  Fig.  189,  the  tower  indicator  A  becomes  deenergized 
thereby  locking  signal  lever  2  in  the  half  reversed  position.  To 


ELECTRIC  LOCKING 


175 


change  the  line-up  in  any  way,  the  latch  on  lever  2  must  be  re- 
turned to  the  full  normal  position.  This  is  done  by  means  of  the 
screw  release.  The  lock  magnet  is  a  relay,  which  becomes 
energized  when  the  lower  contact  of  the  screw  release  is  closed 
through  a  circuit  not  controlled  by  the  indicator.  As  soon  as  the 
lower  contact  is  made,  the  latch  on  lever  2  may  be  returned  to  the 


.*. 


FIG.  188. — Approach  locking. 

full  normal  position,  allowing  for  a  change  in  line-up  of  the  tracks. 
When  the  lower  contact  is  made,  the  upper  contact  is  broken. 
The  upper  contact  must  be  closed  again  by  the  screw  release 
before  the  distant  signal  can  be  cleared. 

Figure  190  is  a  form  of  approach  locking  with  semi-automatic 
control  of  the  power  distant  signal  through  the  contact  of  the 
tower  indicator  with  relief  for  changing  the  line-up  by  means  of 


.1 

* 

"  : 

:  :; 

1  

•i 

- 

;v.v::r: 

r 

•n 

/ 

^ 

, 

L 

* 

.- 

UL 

' 

3 

•  h 

<l"t-  -*!1- 

*-n 

FIG.  189. — Approach  locking. 

the  screw  release.  Distant  signal  D  is  cleared  as  soon  as  home 
signal  2  is  cleared  by  a  current  from  battery  A  through  upper  con- 
tact of  screw  release  R,  contact  on  hard  rubber  drum  of  lock  N, 
front  contact  of  second  armature  /,  circuit  breaker  M,  line  relay 
L,  and  return  to  A,  energizing  line  relay  L.  When  the  relay  L 
becomes  energized,  the  local  circuit  through  battery  B  is  complete 


176 


RAILWAY  SIGNALING 


to  operate  signal  D  to  clear.  The  distant  signal  goes  to  caution 
as  soon  as  a  train  enters  the  section  G-H.  When  there  is  no  train 
in  this  section,  the  track  indicator  J  will  indicate  clear  only  pro- 
vided the  towerman  has  placed  signal  lever  2  in  its  normal  posi- 
tion after  the  passage  of  the  last  train. 

The  signal  lever  2  may  be  returned  to  its  normal  position  at  any 
time,  but  its  latch  cannot  be  released  until  the  block  G-K  is  un- 
occupied and  the  distant  signal  is  placed  at  caution.  This  prevents 
the  towerman  from  quickly  taking  the  signals  away  from  a  train 
after  they  have  been  accepted  and  throwing  a  derail  in  front  of  the 
train.  If  the  block  G-K  is  occupied  by  a  train  and  the  lever 
latch  2  is  in  a  half  reversed  position,  it  cannot  be  restored  to  a  full 
normal  position  except  the  train  move  out  of  the  block  or  the 
towerman  use  his  screw  release. 


FIG.   190. — Approach  locking. 

115.  Route  Locking. — The  Railway  Signal  Association's  defi- 
nition of  route  locking  is:  "Electric  locking  taking  effect  when 
a  train  passes  a  signal  and  adapted  to  prevent  manipulation  of 
levers  that  would  endanger  the  train  while  it  is  within  the  limits 
of  the  route  entered. "  It  is  an  extension  of  section  locking  such 
that  all  switches  and  derails  within  the  limits  of  the  track  to  be 
protected  by  route  locking  are  locked  automatically  by  a  train 
entering  the  route  and  remain  so  locked  until  the  train  leaves  the 
route.  It  should  take  effect  when  the  train  passes  the  first  signal 
on  the  route.  Some  means  should  be  provided  that  the  route 
line-up  may  be  changed  should  a  train  stop  in  the  route,  but  it 
must  be  a  slow  process  requiring  a  time  element  for  protection. 
A  hand  or  time  release  is  used  in  such  instances.  Figure  191 
shows  an  example  of  both  approach  and  route  locking. 


ELECTRIC  LOCKING 


111 


In  this  figure  signal  3  in  a  proceed  position  presupposes  that 
F.P.L.5  and  switches  4  and  6  are  in  proper  position  for  main  line 
movement  from  A  towards  D.  Before  either  4  and  6  can  be 
changed  for  a  different  line-up,  it  is  necessary  to  place  lever  3  and 
then  5  in  the  full  normal  position.  As  soon  as  the  train  enters 
section  A  the  approach  indicator  AB  becomes  deenergized, 
deenergizing,  in  turn,  the  lock  magnet  on  lever  3.  The  towerman 
may  return  lever  3  as  far  as  it  will  go  towards  its  normal  position, 
but  he  cannot  release  the  latch  until  AB  becomes  energized  again, 
which  will  be  when  the  train  passes  out  of  B  into  C.  He  cannot 
move  4  and  6  until  the  latch  on  3  is  released.  Furthermore,  he  can 
not  change  either  switch  while  a  train  is  in  C  because  of  section 
locking. 


FIG.  191. — Approach  and  route  locking.     R.  S.  A.  plan  1149. 

116.  Sectional   Route    Locking. — Sectional    route    locking  is 
defined  by  the  Railway  Signal  Association  as:  " Route  locking  so 
arranged  that  a  train  in  clearing  each  section  of  the  route  releases 
the  locking  affecting  that  section. " 

By  this  system  as  soon  as  the  train  enters  the  route,  all  the 
signals,  switches,  and  derails  on  that  route  are  locked  as  before; 
but  as  soon  as  each  section  is  cleared  by  the  train,  the  locks  in  that 
section  are  released.  This  finds  its  best  service  in  busy  terminals, 
where  extraordinary  protection  is  required,  but  where  the  train 
movements  are  so  frequent  as  to  prohibit  the  long  time  intervals. 

117.  Stick  Locking. — The  Railway  Signal  Association  defines 
stick  locking  as:  " Electric  locking  taking  effect  upon  the  setting 
of  the  signal  for  a  train  to  proceed,  released  by  a  passing  train, 
and  adapted   to    prevent   manipulation   of   levers   that   would 

endanger  an  approaching  train. " 
12 


178 


RAILWAY  SIGNALING 


Stick  locking  does  not  depend  upon  the  presence  of  a  train,  but 
becomes  effective  upon  the  reversal  of  the  home  signal  lever.  It 
remains  effective  until  the  train  passes  the  home  signal  into  the 
releasing  section;  and  unless  the  towerman  returns  the  lever  to  its 
normal  position  while  the  train  occupies  this  releasing  section,  he 
must  use  his  hand  or  time  release  to  do  so.  Figure  192  is  an 
example  of  stick  locking,  which  involves  the  use  of  a  stick  relay. 
This  is  Railway  Signal  Association  plan  1151  with  some  lettering 
added  to  assist  in  the  explanation,  and  the  floor  push  substituted 
for  the  latch. 

When  the  home  signal  lever  3  of  this  plan  is  reversed,  the 
circuit  is  broken  by  circuit  breaker  F  on  signal  3  and  the  stick 
relay  K  becomes  deenergized.  This,  in  turn,  breaks  the  circuit 
from  battery  E  through  the  second  contact  of  R,  wire  T,  lock 


L       D 


FIG.   192.— Stick  locking. 

magent  0,  floor  push,  contact  of  time  release,  contact  on  relay  K 
to  battery  E,  deenergizing  O.  When  the  train  enters  the  block  C, 
track  relay  R  becomes  deenergized,  and  if  the  signal  lever  is 
restored  to  normal  before  the  train  leaves  the  section  C,  relay  K 
will  be  reenergized  through  the  back  contact  of  R.  While  the 
lever  may  be  restored  to  the  normal  position,  its  latch  cannot  be 
released  until  unlocked  by  0.  R  will  become  energized  as  soon 
as  the  train  leaves  the  section  C,  and  immediately  the  lock  0 
becomes  energized  unlocking  the  latch  and  allowing  it  to  fall  to  its 
normal  position.  The  fact  to  be  observed  is,  however,  that  the 
latch  cannot  be  released  in  this  manner  unless  the  lever  is  placed 
in  its  normal  position  while  a  train  is  in  section  C.  If  the  signal- 
man neglects  to  restore  the  lever  to  normal  while  the  section  is 
occupied  by  the  train,  or  if  he  lines  up  a  route  and  the  train  for 
some  reason  or  another  does  not  come  into  the  interlocked  section, 
or  if  he  lines  up  a  route  and  decides  to  change  it  to  another,  he 
must  use  his  hand  release  to  do  so.  In  the  first  instance,  this 


ELECTRIC  LOCKING 


179 


penalizes  him  for  his  negligence,  and  in  the  last  instance  it  pre- 
vents him  from  throwing  a  derail  in  front  of  a  train  after  it  has 
passed  the  distant  signal  giving  a  clear  indication.  The  time 
element  involved  should  be  enough  to  allow  the  train  to  be  over 
the  crossing  and  gone  or  to  allow  the  train  to  come  to  a  stop 
before  it  reaches  the  home  signal. 

118.  Stick  Relay. — A  stick  relay,  represented  by  Fig.  193,  is  so 
connected  that  its  armature  and  front  contact  are  used  to  com- 
plete the  circuit  that  energizes  its  own  coils.  A  circuit  from 
battery  B  through  wires  1,  2,  and  5,  must  be  provided  originally 
to  energize  the  relay  R.  When  A  is  picked  up  another  route 
formed  is  from  battery  B  through  wires  3,  4,  and  5;  and  the  cur- 
rent will  continue  to  flow  through  it  even  though  the  original  cir- 
cuit be  broken  at  C.  If  the  "stick"  circuit  is  broken  at  any  point, 


0 

" 


p— 


FIG.  193. — Stick  relay. 

as  by  the  deenergizing  of  a  track  relay  where  its  armature  forms 
a  part  of  the  stick  circuit,  the  relay  R  becomes  deenergized 
and  the  armature  A  will  not  pick  up  until  the  original  circuit 
is  closed. 

119.  Check  Locking. — Where  two  interlocking  plants  are 
located  a  comparatively  short  distance  apart  on  a  single-track  road, 
it  becomes  necessary  at  times  to  so  interlock  levers  in  the  two 
towers  that  conflicting  movements  of  trains  will  be  impossible. 
Such  an  arrangement  is  called  check  locking.  Figure  194  shows 
such  a  check  locking  circuit  where  there  is  no  preference  as  to  the 
direction  of  traffic.  There  is  a  check  lock  lever  in  each  plant  A 
and  Z  so  interlocked  with  the  signal  levers  that  the  signal  levers 
cannot  be  placed  in  the  proceed  position  until  their  respective 
check  lock  levers  have  been  moved  to  the  full  reverse  position. 
By  referring  to  Fig.  194  it  will  be  seen  that  as  only  one  of  the 
check  lock  levers  can  be  placed  in  the  full  reverse  position  at  a 
time,  it  will  be  impossible  to  clear  but  one  signal  at  a  time;  that  is, 


180 


RAILWAY  SIGNALING 


20  cannot  be  cleared  while  1  is  cleared.  As  the  signal  lever  at 
both  A  and  Z  when  reversed,  locks  its  check  lever  reversed,  the 
check  lock  lever  must  be  fully  reversed  before  the  signal  lever  can 
be  reversed.  The  two  check  lock  levers  are  each  equipped  with  a 
half  reverse  lever  lock  that  can  be  energized  only  when  the  two 
sets  of  devices  are  in  a  certain  position.  The  signalman  in  tower 
A  may  reverse  his  check  lever  lock  to  the  reverse  indication  point, 
but  he  cannot  move  it  any  farther  until  the  lever  lock  becomes 
energized  in  the  following  manner. 

Current  from  the  battery  at  Z  flows  through  the  normal  circuit 
controller  of  the  check  lock  lever  at  Z,  then  through  the  front 
contact  of  the  track  relay  X,  and  on  through  the  reverse  circuit 


FIG.  194. — Check  locking  circuit, 
direction  of  traffic. 


For  use  where  there  is  no  preference  as  to 
(General  Railway  Signal  Co.) 


controller  of  the  check  lock  lever  at  A,  and  to  the  lever  lock 
itself.  After  the  lock  becomes  energized,  the  lever  may  be 
placed  in  the  full  reverse  position,  whence  the  signal  lever  1  may 
be  cleared.  The  check  lock  lever  at  Z  may  be  reversed  to  the 
indication  point,  but  it  cannot  be  reversed  beyond  that  point 
because  its  lock  magnet  cannot  be  energized.  Thus  signal  20 
must  remain  at  the  stop  indication  until  1  is  restored  to  normal. 
As  only  one  of  the  signals  can  be  cleared  at  a  time,  traffic  can  be 
given  a  proceed  indication  in  only  one  direction  at  a  time.  On 
account  of  the  fact  that  the  relay  X,  operated  by  the  track  cir- 
cuit between  the  two  towers,  controls  the  check  lever  lock  cir- 
cuits, it  is  impossible  to  reverse  the  signal  indications  while  a 
train  occupies  the  track  between  A  and  Z. 

120.  Union  Electro-mechanical  Slot. — The  up-and-down  rod, 
which  is  pushed  upward  to  clear  the  signal,  is  made  in  two  parts, 
A,  and  B,  Fig.  195,  and  is  so  connected  by  the  electro-mechanical 


ELECTRIC  LOCKING 


181 


FIG.  195. — Union  electro-mechanical  slot. 


182 


RAILWAY  SIGNALING 


slot  mechanism  that  when  the  magnet  M  is  energized  the  signal 
can  be  cleared,  but  when  it  is  deenergized  the  signal  cannot  be 
cleared  even  though  the  portion  of  the  rod  A  be  raised.  The 
two  bars,  L  and  T7,  form  a  toggle  hinged  at  0,  G,  and  S.  Any 


FIG.   196. — Hall  electro-mechanical  slot. 

upward  thrust  on  A  tends  to  throw  the  roller  G  to  the  left  on 
account  of  the  weight  of  the  signal  arm  and  the  rod  B.  When 
the  magnet  M  is  energized  this  side  thrust  is  resisted  by  another 
toggle  hinged  at  N,  P,  and  Q  and  held  in  position  by  the  armature 
R.  Thus,  the  up-and-down  rod  is  made  rigid  and  the  signal 


ELECTRIC  LOCKING 


183 


can  be  cleared.  As  the  three  points,  N,  P,  and  Q,  are  not  in 
line,  the  two  pieces  N-P  and  P-Q  will  buckle  as  soon  as  the  magnet 
becomes  deenergized  if  there  is  any  pressure  applied,  during 
which  time  the  signal  arm  cannot  be  cleared. 

At  the  top  of  the  encasing  iron  box  is  a  dashpot  installed 
to  relieve  the  force  of  the  blow  as  the  blade  comes  to  the  stop 
position.  The  magnet,  M ,  is  controlled  by  track  circuits  and  is 
energized  continuously  except  when  the  track  section  is  occupied 
by  a  train.  The  spring  F  tends  to  hold  the  lever  L  in  position 


FIG.  197. — Tower  indicator. 

against  T  when  the  rod  A  is  normal  so  that  the  magnet  can  get 
control  of  its  armature  R.  The  lever  must  be  placed  in  its 
normal  position  again  before  the  signal  can  be  cleared. 

121.  Hall  Electro-mechanical  Slot.— In  the  Hall  type  of  slot, 
shown  in  Fig.  196,  A  represents  the  lower  portion  of  the  up-and- 
down  rod,  or  that  portion  that  connects  directly  to  the  signal 
lever,  and  B  the  portion  fastened  to  the  signal  arm.  A  is  large 
enough  to  allow  B  to  slide  inside  it.  A  pin  C  passes  through  the 
lower  end  of  B  and  extends  far  enough  out  on  each  side  to  engage 
the  outside  rod  at  the  top  of  the  slot  S.  Both  rods  are  notched 
at  N  to  receive  the  point  of  the  latch  L.  M  is  an  electro-magnet 
with  an  armature,  R,  connected  to  the  arm  E.  When  the 
magnet  is  energized  the  arm  E  presses  against  the  roller  D  on  the 


184 


RAILWAY  SIGNALING 


lower  end  of  the  latch  and  causes  the  point  G  to  engage  both  A 
and  B  so  that  when  A  is  raised  to  clear  the  signal,  B  moves  also 
and  the  signal  goes  to  clear.  Should  a  train  enter  the  block 
when  the  signal  is  clear,  the  magnet,  M,  would  immediately 
become  deenergized  allowing  E  to  move  away  from  D,  whereas 
the  weight  of  the  signal  arm  and  rod  B  would  force  the  point  G 
out  of  the  notch  in  rod  B  and  the  signal  would  go  to  the  stop 
position.  The  spring  F  tends  to  keep  the  arm  E  and  the  armature 
R  in  contact  with  the  magnet  M .  The  signal  cannot  be  cleared 
again  until  the  lever  is  placed  in  the  normal  position  and  the 
magnet  is  energized.  K  is  an  ordinary  dashpot  used  to  relieve 


FIG.  198. — Tower  indicators.     (Hall  Switch  and  Signal  Co.) 

the  shock  of  the  signal  when  the  blade  goes  to  stop.  The 
magnet  M  is  controlled  by  track  circuits  and  is  energized  con- 
tinuously except  when  the  track  section  is  occupied  by  a  train. 
The  semi-automatic  feature  of  these  signals  permits  them  to 
go  to  the  stop  position  automatically  even  though  the  operator 
does  not  restore  his  lever  to  the  normal  position,  an  arrangement 
that  operates  on  the  side  of  safety  to  prevent  a  following  train 
from  entering  the  block  until  authorized  to  do  so.  The  magnet 
is  controlled  by  a  short  track  section;  and  so  long  as  the  track 
circuit  is  not  occupied  by  a  train  the  signal  can  be  cleared,  but 
as  soon  as  a  train  enters  the  section  the  slot  magnet  becomes 
deenergized  allowing  the  signal  to  go  to  the  stop  position. 


ELECTRIC  LOCKING  185 

122.  Tower  Indicators. — Tower  indicators  are  used  to  notify 
towermen  of  the  approach  of  trains  and  to  aid  them  in  following 
more  closely  the  movements  of  trains  through  interlocking 
plants  where  route  and  other  locking  is  practiced.  The  informa- 
tion concerning  the  approach  of  trains  is  generally  given  by 
disc  indicators;  while  that  concerning  the  movements  over 
track  sections  through  interlocked  territory  is  usually  given  by 
semaphore  indicators.  These  are  ordinarily  located  on  the  wall 
of  the  tower  where  they  can  be  easily  seen  by  towermen. 


CHAPTER  X 


MANUAL  BLOCK  SYSTEM 

A  manual  block  system  is  one  in  which  the  signals  or  other 
devices  governing  thfe  spacing  of  trains  are  operated  by  hand. 

There  are  three  ways  of 
applying  the  system;  Man- 
ual Block,  Controlled- 
manual  Block,  and  Electric 
Train  Staff. 

THE  MANUAL  BLOCK 

123.  General  Description. 

The  manual  block  is  noth- 
ing more  nor  less  than 
the  ordinary  telegraph  or 
telephone  block  where  an 
operator  at  one  station  is 
free  to  clear  his  signal  at 
any  time  without  electrical 
or  mechanical  check  from 
any  other  station.  Ad- 
jacent operators  communi- 
cate by  telegraph  or 
telephone  and  clear  or  hold 
trains  according  to  the  rules 
in  force  on  the  particular 
road.  The  blocks  are  gen- 
erally the  distance  between 
ordinary  commercial  sta- 
tions, but  occasionally  on 
busy  lines  intermediate 
towers  are  built  in  order  to 
shorten  the  blocks.  The 

FIG.   199.  — R.  s.  A.  double-arm  upper    signals  are  given  by  train- 
quadrant  tram-order  signal.  . 

order  boards,   which  stand 

in  front  of  the  station  building  or  tower.  One  arm  of  the  signal 
governs  movements  of  trains  in  one  direction  and  the  other  arm 
those  in  the  opposite  direction. 

186 


MANUAL  BLOCK  SYSTEM  187 

There  are  three  roundels  or  glasses  in  each  signal,  and  one 
lamp  serves  the  purpose  of  all  of  them.  Usually  the  signal 
indicates  either  stop  or  proceed,  but  a  few  roads  use  the  45-degree 
position  for  giving  crews  an  indication  for  a  19  order.  The  posi- 
tions of  the  blades  and  the  colors  of  the  lights  correspond  to  those 
in  use  for  ordinary  signaling  purposes.  Figure  199  is  the  type 
recommended  by  the  Railway  Signal  Association  and  operates  in 
the  upper  quadrant. 

The  telegraph  method  of  signaling  has  no  check  whatever  on 
broken  rails  or  open  switches  as  some  of  the  other  methods  have. 
Although  the  system  is  still  in  use  on  a  great  many  branch  lines 
and  smaller  roads,  there  are  so  many  chances  for  accidents  to 
trains  through  mistakes  made  by  operators  that  other  systems 
have  been  installed  which  have  more  checks  to  safeguard  the 
train  movements. 

THE  CONTROLLED-MANUAL  BLOCK 

124.  General  Description.— In  the  controlled-manual  block  sys- 
tem the  signals  are  operated  mechanically,  but  are  so  controlled 
electrically  that  the  signal  at  one  station  cannot  be  cleared  without 
the  aid  of  the  operator  at  an  adjacent  station.  If  operator  A 
desires  to  clear  his  signal  for  an  approaching  train  to  pass  into  a 
block,  he  must  communicate  with  the  opera  tor  B  at  the  other  end 
of  that  block,  and  request  him  to  assist  in  releasing  the  lock  on  his 
signal  mechanism.  If  B  is  in  position  to  permit  the  train  to 
enter  the  block,  he  complies  with  the  request,  after  which  A  may 
proceed  to  clear  his  signal. 

Figure  200  shows  a  form  of  controlled-manual  machine  made 
by  the  General  Railway  Signal  Company.  To  move  a  train  from 
A  to  B,  the  operator  at  A  signals  B  by  means  of  a  bell  to  close  the 
circuit  at  3,  Fig.  201,  in  his  controller  by  turning  arm  12.  At 
the  same  time,  A  closes  10  by  operating  his  lever  13.  The  circuit 
being  then  complete,  current  will  flow  from  battery  28  through 
wire  1,  contacts  2-2  of  the  lock  L,  contacts  3,  wires  4  and  5, 
contacts  6,  wire  7,  indicator  magnet  29,  wire  8,  indicator  magnet 
30,  wire  9,  contacts  10,  wire  11,  electro-magnet  31,  and  to  the 
ground.  When  magnet  31  becomes  energized,  the  lock  14  is 
lifted  and  lever  15  may  be  withdrawn  unlocking  lever  19.  When 
lever  19  is  turned  one-half  a  revolution  the  signal  is  cleared.  It  is 
restored  to  the  stop  position  by  completing  the  revolution.  A 
ratchet  wheel,  18,  is  provided  to  insure  that  the  handle  19  be 


188 


RAILWAY  SIGNALING 


turned  only  in  one  direction.     The  pipe  that  operates  the  signal 
is  connected  directly  to  the  crank  21.     There  is  a  lug,  22,  on  the 


FIG.  200. — Controlled-manual  station  block  instrument. 


FIG.  201. — Wiring  diagram  for  controlled-manual  system. 

ratchet  wheel  18,  that  when  the  signal  is  returned  almost  to  the 
stop  position  engages  the  arm  23  and  forces  the  lock  17  into  its 


MANUAL  BLOCK  SYSTEM  189 

seat  requiring  that  the  signal  be  again  unlocked  before  it  can  be 
cleared. 

Besides  being  a  check  on  the  operators,  there  are  different 
degrees  of  track  protection  afforded  by  the  controlled-manual 
system  where  track  circuits  are  installed.  The  length  of  the 
track  circuit  may  be,  in  some  cases,  merely  enough  to  protect 
switches  and  to  control  semi-automatic  signals  at  each  end  of  the 
block;  while  it  may  extend  entirely  through  the  block,  in  other 
cases,  giving  better  protection  against  broken  rails.  The  ordi- 
nary train-order  boards  are  used  where  there  are  no  track  cir- 
cuits, and  slotted  signals  where  there  are  track  circuits.  A 
slotted,  or  semi-automatic  signal,  is  one  cleared  by  mechanical 
or  other  means,  but  is  put  to  danger  automatically  by  the  train 
entering  the  block.  These  semi-automatic  signals  are  equipped 
with  electro-mechanical  slots. 

THE  ELECTRIC  TRAIN  STAFF 

125.  General. — The  staff  system  is  one  form  of  the  controlled- 
manual  system  of  block  signaling  and  is  applied  only  to  single- 
track  operation.  The  system  finds  its  best  application  on  roads 
with  heavy  traffic,  being  used  principally  in  dangerous  places,  as 
at  bridges  and  tunnels  on  non-electrified  territory  and  at  points 
where  it  is  not  feasible  to  install  track-circuit  signaling.  The 
road  is  divided  into  blocks  of  5  or  6  miles  in  length;  usually  the 
existing  stations  will  suffice  to  form  about  the  proper  length  of 
block  when  the  staff  system  is  installed,  although  occasionally  an 
additional  station  will  need  to  be  supplied  in  order  to  expedite 
train  movements.  Two  staff  machines  that  are  exactly  alike 
are  provided  for  each  block,  one  stationed  in  the  tower  at  each 
end  of  the  block.  The  tWo  machines  are  so  connected  by  wires 
that  they  are  interdependent  in  operation. 

The  train  is  given  a  metal  staff  and  this  eliminates  the  necessity 
of  a  written  train  order.  No  train  is  allowed  to  proceed  into  a 
block  unless  the  engineman  has  a  staff.  Only  one  staff  can  be 
taken  out  of  either  instrument  at  a  time;  and  when  one  is  out, 
both  instruments  are  automatically  locked  and  remain  locked 
until  that  staff  is  returned  to  one  or  the  other  of  the  two  machines. 
The  engineman  must  take  a  new  staff  at  the  beginning  of  each 
block  and  deliver  it  at  the  end  of  that  same  block.  The  staffs 
are  made  of  steel  rods,  %  in.  in  diameter  and  6  in.  in  length,  so 
cut  with  such  a  series  of  annular  grooves  that  those  used  in  one 


190 


RAILWAY  SIGNALING 


block  will  not  fit  the  instruments  of  the  adjacent  blocks.  The 
instruments  are  duplicated,  but  the  distance  between  duplicate 
pairs  is  great  enough  to  prevent  the  staffs  from  being  carried 
over. 

126.  Operation  of  the  Absolute  Staff  Instrument.1 — In  the 
description  of  the  staff  equipment  made  by  the  Union  Switch  & 
Signal  Company,  a  train  is  considered  to  move  from  station  X  to 
station  F,  Fig.  202.  The  operator  at  X  presses  his  bell  key  A  the 
number  of  times  prescribed  in  the  bell  code,  and  rings  the  bell  L 
at  F,  Fig.  204,  from  the  positive  side  of  the  battery  through  the 
circuit  1,  2,  3,  4,  5,  6,  7,  8,  9,  10,  11,  12,  13,  14,  15,  16,  17,  and  re- 


Line  6-* 
FIG.  202. — Wiring  diagram  for  absolute  train  staff  system.     (Signal  Dictionary,) 

turn  to  the  battery.  The  operator  at  F  acknowledges  the  call 
by  closing  his  bell  key  A,  thereby  ringing  the  bell  L  at  X  through 
the  circuit  19,  20,  21,  8,  7,  6,  5,  4,  22,  23,  24,  25,  17,  16,  15,  14,  13, 
26;  and  as  he  continues  to  hold  it  closed,  he  deflects  the  "current 
indicating  needle,"  F,  Fig,  203,  at  X  to  the  right.  Thus  in- 
formed that  F  has  furnished  the  necessary  current,  X  proceeds  to 
remove  the  staff  by  turning  the  preliminary  spindle  handle  B, 
Fig.  203,  to  the  right  as  far  as  it  will  go.  This  raises  the  armature 
J,  Fig.  206  up  to  the  magnets  K,  transferring  the  current  from 
bell  L  to  the  magnet  K-88  through  the  circuit  19,  20,  21,  8,  7,  6,  5, 
4,  22,  23,  27,  28,  25,  17,  16,  15,  14,  13,  26,  and  at  the  same  time 
closing  the  circuit  on  magnet  K-36Q  through  the  circuit  1,  2,  29, 
1  From  the  Signal  Dictionary,  p.  38. 


MANUAL  BLOCK  SYSTEM 


191 


30,  28,  25,  after  which  the  preliminary  spindle  handle  is  permitted 
automatically  to  return  to  its  normal  position.  This  unlocks 
the  revolving  drum,  (7,  Fig.  206,  and  indicates  the  fact  by  dis- 
playing a  white  instead  of  a  red  disc  in  the  indicator,  H,  Fig.  205. 
The  operator  now  moves  the  end  staff,  E,  Fig.  203,  up  the  vertical 
slot  into  engagement  with  the  drum,  C,  Fig.  206,  (the  outer  guard, 
N,  Fig.  205,  having  first  been  turned  to  the  right  position),  re- 
volves the  latter  through  a  half  turn,  using  the  staff  as  a  handle, 


FIG.   203.— Absolute  staff 
instrument. 


FIG.    204. — Rear   view   of    absolute 
staff  instrument. 


and  finally  withdraws  the  staff  through  the  opening  at  M,  Fig. 
203.  In  making  the  half  turn,  the  drum,  C,  Fig.  206,  has  re- 
versed the  polarity  of  the  operating  current,  thereby  throwing  the 
instruments  at  X  and  Y  out  of  synchronism  with  each  other  and 
moving  the  "staff  indicating  needle,"  G,  at  X,  Fig.  207  from 
"Staff  In"  to  "Staff  Out,"  Immediately  on  withdrawing  the 
staff,  the  operator  at  X  once  more  presses  his  bell  key  A,  which 
indicates  to  the  operator  at  F,  by  moving  his  needle  from  "Staff 
In"  to  "Staff  Out"  that  the  operation  is  completed.  He  then 
prepares  to  deliver  the  staff  to  the  train. 


192 


RAILWAY  SIGNALING 


The  magnet  K,  Fig.  202  has  two  separate  coils,  K-360  energized 
by  the  local  battery  and  K-88  energized  by  the  line  battery. 
The  polarity  of  the  current  through  K-360  is  never  changed, 
but  that  through  K-88  is  changed  every  time  a  staff  is  put  in  or 
taken  out  of  either  instrument.  When  the  currents  in  both  coils 
have  the  same  polarity,  there  is  no  attraction  for  the  armature. 


FIG.  205. — Front  view  of  staff  instrument  in  con- 
dition for  removal  of  staff. 


FIG.  206.— Staff  instrument 
with  armature  up. 


When  the  current  is  reversed  in  one  coil,  the  lines  of  force  oppose 
each  other  and  the  armature  being  brought  to  the  point  of  attrac- 
tion, is  held  there.  With  the  staff  out,  if  an  attempt  should  be 
made  to  release  another  staff  by  turning  the  preliminary  handle, 
the  circuit  closed  would  be  from  the  positive  side  of  the  battery 
through  19,  20,  21,  bell  key  A  closed,  8,  7,  6,  5,  17,  25,  28,  27, 
23,  22,  4,  16,  15,  14,  13,  26,  to  the  negative  side  of  the  battery 


MANUAL  BLOCK  SYSTEM 


193 


at  Y,  with  the  polarity  of  the  current  flowing  through  magnet 
K-88  reversed.  By  comparing  this  circuit  with  the  one  des- 
cribed for  releasing  the  staff  it  will  be  seen  that  in  the  former 
the  currents  flowing  through  magnets  K-36Q  and  .K-88  oppose 
each  other,  and  in  the  latter  they  do  not,  which  prevents  the 
releasing  of  the  second  staff. 


-G 


FIG.  207. — Front  view  when  a  staff  is  released  or 
about  to  be  replaced. 


FIG.  208. — Side  elevation 
of  staff  machine. 


On  arrival  of  the  train  at  Y  the  crew  delivers  the  staff  to 
the  operator,  who  places  it  in  the  opening  M,  Fig.  203,  of  his 
instrument,  having  first  turned  the  outer  guard,  N,  Fig.  205, 
to  place.  He  moves  the  staff  into  engagement  with  the  drum  D, 
Fig.  206,  revolves  the  drum  through  one-half  turn  to  the  right, 
using  the  staff  as  a  handle,  and  allows  the  staff  to  roll  down  the 
spiral.  He  then  presses  his  bell  key  the  prescribed  number  of 

13 


194 


RAILWAY  SIGNALING 


times,  thus  notifying  X  that  the  train  is  out  of  the  section,  which 
operation  also  moves  the  "staff  indicating  needle"  at  X  from 
''Staff  Out"  to  "Staff  In."  The  operator  at  X  presses  his  bell 
key  in  acknowledgment,  and  by  so  doing  moves  the  "staff  indi- 
cating needle"  at  Y  from  "Staff  Out"  to  "Staff  In."  The 
machines  are  now  synchronized  and  another  staff  can  be  obtained 
from  either  in  the  manner  outlined  above. 

If  the  speed  of  the  train  does  not  exceed  25  miles  an  hour, 
the  staffs  removed  from  the  instruments  by  the  block  operators 
are  delivered  to  the  enginemen  by  hand  by  means  of  a  small  hoop 


FIG.  209. — Staff  catcher  and  deliverer. 

formed  of  a  piece  of  rubber  hose.  If  the  speed  is  more  than  25 
miles  an  hour,  they  are  delivered  by  means  of  a  staff  catcher  that 
operates  something  on  the  order  of  a  mail  crane,  as  shown  in  Fig. 
209.  The  staffs  are  returned  to  the  operators  in  a  similar  manner. 
127.  The  Permissive  Staff. — Where  several  trains  are  allowed 
to  follow  one  another  at  short  intervals  through  the  block,  they 
operate  under  what  is  termed  the  permissive  system.  A  permis- 
sive attachment,  shown  in  Fig.  210,  is  installed  at  each  end  of 
each  block  in  connection  with  the  absolute  machine  with  only 
one  permissive  staff  for  the  two  instruments.  To  move  a  series 
of  trains  from  X  to  Y  this  staff  must  be  at  X.  The  permissive 
staff,  represented  by  Fig.  211^,  is  made  by  passing  a  double 
steel  rod  through  1 1  separate  and  removable  discs,  called  tablets. 


MANUAL  BLOCK  SYSTEM 


195 


There  is  an  additional  disc  fastened  to  the  end  of  the  rod  making 
altogether  12  separate  pieces  in  the  staff.  To  operate  the 
machine  one  of  the  regular  staffs  used  in  the  absolute  system  is 
removed  from  the  instrument  at  X  and  is  used  to  unlock  the 
permissive  attachment.  The  withdrawal  of  the  permissive 
staff  locks  the  absolute  staff  in  the  permissive  case  and  it  cannot 
be  removed  until  the  permissive  staff  is  returned  to  the  case  at 
one  end  or  the  other  of  the  block. 


FIG.  210. — Permissive  and  pusher  attachments. 

As  the  trains  enter  the  block,  each  one  except  the  last  takes 
one  tablet,  thus  providing  that  as  many  as  12  trains  may  go  in 
one  direction  should  there  not  be  occasion  in  the  meantime  to 
send  one  in  the  opposite  direction.  If  there  should  be  less 
than  12,  the  last  one  would  take  all  that  is  left  of  the  staff 
including  the  steel  rod.  These  pieces  are  all  delivered  by  the 
trains  to  the  operator  at  Y,  the  leaving  end  of  the  block.  He 
assembles  them  again  into  a  single  unit  and  places  them  in  his 
permissive  attachment.  This  allows  the  absolute  staff  to  be 
released;  and  as  soon  as  it  is  returned  to  the  absolute  machine, 
an  absolute  staff  may  be  removed  at  either  end  of  the  block.  A 
train  may  now  move  in  either  direction  with  an  absolute  staff 


196 


.RAILWAY  SIGNALING 


and  from  Y  to  X  with  the  permissive  staff.  If  it  is  anticipated 
that  another  series  of  trains  will  move  from  X  to  F,  the  first 
engineman  going  from  Y  to  X  will  use  the  permissive  staff 
instead  of  an  absolute,  for  the  permissive  staff,  as  a  whole,  con- 
fers the  same  rights  as  an  absolute  staff.  The  operator  at  X  will 
then  be  prepared  to  handle  the  trains  by  the  permissive  system. 
An  engineman  having  any  part  of  the  permissive  staff  is  certain 


FIG.  211. — Staffs  and  staff  pouches. 

that  he  will  not  meet  a  train,  but  he  will  expect  to  find  one 
preceding  him  unless  he  has  the  first  tablet,  or  one  following 
him  unless  he  has  the  rod  and  possibly  some  remaining  tablets. 
128.  Intermediate  Siding  and  Junction  Instruments. — At 
sidings  between  stations  a  special  staff  machine  may  be  installed 
to  govern  movements  of  trains  that  meet  there.  If  there  is  a 
train  to  leave  X  for  the  siding  between  X  and  F,  the  operator  at 
F  will  unlock  the  instrument  at  X  and  allow  a  staff  to  be  removed. 
This  staff  is  handed  to  the  engineman  and  when  the  train  arrives 


MANUAL  BLOCK  SYSTEM  197 

at  the  siding  the  staff  is  used  to  unlock  the  switch.  After  the 
train  is  entirely  in  the  clear  on  the  siding  and  the  switch  is  locked, 
the  staff  is  placed  in  the  special  staff  instrument  there,  synchron- 
izing the  instruments  at  X  and  Y. 

If  there  is  a  junction  point  between  the  two  stations  X  and  Y, 
a  special  junction  instrument  is  often  installed  there  when  there 
is  not  enough  traffic  on  the  branch  line  to  warrant  a  com- 
plete station  and  set  of  instruments.  The  movements  from 
the  point  X  or  Y  to  the  junction  and  into  the  branch  line  are 
made  just  as  are  those  explained  above. 

When  a  train  is  to  leave  a  branch  line  or  siding  for  the  main 
line,  the  crew  calls  both  X  and  Y.  The  operators  at  these  two 
stations  acting  together  can  release  a  staff  in  the  junction  or 
switch  instrument.  When  this  is  removed  every  machine  in  that 
block  is  locked  and  remains  so  until  the  staff  is  returned  to  any 
one  of  them.  After  the  crew  unlocks  the  switch  with  this  staff, 
the  train  pulls  out  on  the  main  track.  The  crew  locks  the  switch 
again  and  takes  the  staff  to  X  or  F,  depending  upon  the  direction 
they  are  traveling. 

129.  Pusher  Attachment. — In  order  to  operate  a  pusher 
engine  a  portion  of  the  distance  between  X  and  Y  and  let  it 
return  to  X,  a  special  pusher  engine  instrument  is  attached  to 
the  absolute  instrument,  Fig.  210.  The  pusher  staff  can  be 
released  only  by  a  staff  from  the  absolute  machine.  Both 
staffs,  however,  can  be  removed  at  one  time.  In  order  to  proceed 
from  X  to  F,  the  operator  at  X  signals  Y  to  release  the  absolute 
staff.  X  removes  this  staff  and  uses  it  to  unlock  the  pusher 
staff.  The  train  takes  the  absolute  staff  and  the  pusher  engine 
the  pusher  staff.  After  the  pusher  engine  has  gone  as  far  as 
necessity  requires,  it  returns  to  X  while  the  train  goes  on  to  Y. 
Both  deliver  their  staffs,  the  one  at  X  and  the  other  at  Y.  No 
other  staff  can  be  removed  from  either  end  of  the  block  until  they 
both  are  returned.  In  Fig.  211,  numbers  1,  2,  3,  and  4  represent 
absolute  staffs  and  5,  6,  7,  and  8  represent  pusher  staffs. 


CHAPTER  XI 
AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK 

GENERAL 

130.  Object. — The  purpose  of  automatic  block  signaling  on 
double  track  is  to  provide  automatically  by  the  trains  themselves 
such  an  interval  between  trains  moving  in  the  same  direction 
over  the  same  route  as  will  secure  safety  and  efficiency  in  opera- 
tion. One  of  the  factors  that  influence  the  efficiency  of  a  block 
system  is  the  length  of  its  blocks.  The  manual  and  controlled- 
manual  systems,  where  the  length  of  block  varies  from  3  to  8  miles, 
provide  for  only  one  train  between  stations  or  towers,  for  there 
can  be  only  one  train  in  a  block  at  one  time.  The  automatic 
block  system,  where  the  average  length  of  block  is  practically  a 
mile,  is  much  more  effective.  It  permits  a  shorter  interval 
between  trains  and  an  additional  factor  of  safety.  Closing  a 
station  or  tower  at  night  has  the  effect  of  rendering  the  manual 
system  still  more  inefficient,  but  has  no  effect  on  the  operation  of 
the  automatic  system.  By  using  automatic  block  signals,  the 
trains  can  in  many  cases,  operate  without  train  orders.  This 
tends  to  eliminate  some  of  the  expense  of  having  operators  to 
deliver  the  orders  and  of  stopping  and  starting  trains  to  receive 
them.  The  same  analysis  of  the  cost  of  starting  and  stopping 
trains  could  be  made  for  automatic  signals  as  for  interlocking. 

Running  trains  over  a  division  in  a  shorter  time  will  not 
only  curtail  the  overtime  wage  far  train  crews,  but  will  also 
give  a  more  intense  service  for  the  train  equipment.  The  same 
number  of  engines  and  cars  will  handle  more  business  in  an  equal 
length  of  time.  The  detection  of  broken  rails  by  means  of 
track  circuits  is  an  item  of  great  advantage. 

Of  the  99,360  miles  of  block  signals  installed  in  the  United 
States  up  to  1919,  36,600  were  automatic.  In  order  to  install  a 
system  of  automatic  block  signals  on  single  or  double  track,  the 
road  is  divided  into  blocks  varying  in  length  from  a  few  hundred 
feet  to  a  few  miles,  depending  upon  the  length  of  trains  and  the 
amount  of  traffic  handled.  The  trains  operate  these  automatic 
block  signals  by  means  of  electric  current  flowing  through  the 
rails  and  through  wires  running  along  the  right-of-way. 

198 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK    199 

131.  Location  of  Signals. — There  are  several  factors  that 
influence  the  spacing  and  location  of  automatic  block  signals. 
Whatever  the  kind  of  train  service  the  road  is  giving,  the  spacing 
between  the  home  and  distant  signals  should  exceed  somewhat 
the  maximum  braking  distance  for  the  highest  speed  attained  in 
that  block.  Since  it  is  one  of  the  functions  of  block  signals  to 
expedite  train  movements,  the  blocks  on  roads  having  dense 
traffic  should  necessarily  be  shorter  than  on  those  having  light 
traffic.  As  trains  run  faster  on  down  grades  than  on  up  grades, 
the  blocks  should  be  longer  going  down.  Trains  should  be  able 
to  cover  blocks  in  about  equal  spaces  of  time.  Signals  should  be 
so  placed  as  not  to  stop  tonnage  trains  on  heavy  grades,  if  possi- 
ble; for  when  they  stop  they  will  generally  experience  some 
difficulty  in  starting  again.  In  terminals  where  trains  are 
frequent,  but  where  their  movements  are  slow,  the  blocks  should 
be  shorter  than  they  are  in  the  open  country.  Signals  should 
stand  as  near  the  beginning  of  curves  as  practicable  in  order  to 
give  the  enginemen  a  chance  to  see  them  as  far  as  possible.  It  is 
much  easier  to  see  them  against  an  open-sky  background  than 
against  trees  or  buildings  or  the  side  of  an  open  cut.  They 
should,  however,  stand  in  front  of  bridges,  water-tanks,  and 
tunnels  and  not  immediately  behind  them.  A  signal  near  a 
station  should  stand  beyond  the  depot  where  the  engineman  can 
see  it  when  he  makes  the  station  stop.  In  such  cases  he  would 
ordinarily  not  start  his  train  until  the  signal  should  go  to  the 
proceed  position. 

From  an  article  entitled  "Automatic  Signal  Locations/7  by 
the  late  C.  C.  Rosenberg,  and  published  in  Volume  II  of  the  Pro- 
ceedings of  the  Railway  Signal  Association,  the  following  para- 
graphs have  been  selected: 

"  In  making  a  survey  for  the  installation  of  automatic  signals,  one  of 
the  greatest  problems  to  be  solved  is  that  of  location,  and  in  order  to 
get  the  best  results,  it  is  necessary  that  the  subject  be  given  careful 
study  and  thorough  consideration  from  every  standpoint. 

"  Signal  Engineers  and  others  in  charge  of  signal  construction  on 
roads  which  have  automatic  signals,  find  that  after  signals  are  placed  in 
service,  some  are  to  a  great  extent  of  little  value  owing  to  poor  sight, 
stalling  of  trains,  etc.,  and  in  some  instances  give  confusing  indications. 
In  order  to  correct  these,  considerable  expense  is  incurred  which  could 
to  a  large  extent  have  been  avoided  if  proper  consideration  had  been 
given  at  the  time  of  locating. 


200  RAILWAY  SIGNALING 

"In  locating,  the  following  conditions  should  be  considered;  the 
relative  relation  of  the  signal  to  sight,  passing  sidings,  crossovers, 
interlocking  plants,  junction  points,  passenger  stations  and  length  of 
block. 

"As  all  railroads  are  not  fortunate  enough  to  have  long  tangents,  it  is 
often  a  serious  problem  to  get  a  good  sight  for  a  location  on  account  of 
obstructions  or  being  placed  in  a  series  of  short  curves ;  it  is  often  neces- 
sary to  lengthen  or  shorten  the  block  in  order  to  get  even  a  fair  sight. 

"At  a  passing  siding,  the  signal  should  be  placed  back  of  the  fouling 
point  of  the  outlet  switch,  so  as  to  protect  a  train  moving  from  the 
siding  to  the  main  track;  while  at  the  same  time  allow  an  approaching 
train  on  main  track  to  advance  one  block  farther  than  if  placed  ahead  of 
the  switch.  No  signal  should  be  placed  immediately  ahead  of  an  outlet 
switch,  and  used  as  a  starting  signal;  but  in  order  to  give  a  train  moving 
from  a  passing  siding  a  starting  signal,  it  should  be  placed  at  a  distance 
far  enough  in  advance  of  the  outlet  that  it  cannot  be  mistaken  by  a 
train  approaching  on  the  main  track  as  its  signal.  The  train  moving 
from  the  siding  to  the  main  track  should  proceed  cautiously  and  under 
full  control  until  the  next  signal  is  reached.  The  proper  location  for  a 
signal  at  the  inlet  of  a  passing  siding  is  within  500  ft.  of  the  switch 
points,  and  the  next  signal  in  rear  should  be  placed  not  more  than  Y± 
mile  from  the  switch,  preferaby  less,  if  it  can  so  be  arranged. 

"No  location  should  be  made  immediately  in  advance  of  a  crossover, 
but  far  enough  in  the  rear  to  protect  the  same  should  the  location  be 
found  to  come  in  the  vicinity  of  such  crossover. 

"Locating  signals  on  the  outside  of  curves  should  be  avoided  as  far 
as  possible;  but  if  this  is  found  necessary,  then  the  masts  should  be  high 
enough  to  place  the  signals  so  that  they  can  be  seen  from  approaching 
trains  over  the  top  of  a  train  passing  in  the  opposite  direction,  or  a  train 
standing  on  a  siding. 

"Telegraph  pole  lines  should,  wherever  practicable,  be  moved  as 
near  the  right-of-way  as  possible  so  as  not  to  obstruct  the  sight  of 
signals.  All  undergrowth  and  overhanging  trees  should  be  kept  trim- 
med, so  that  a  good  view  can  always  be  obtained. 

"In  order  to  give  extra  protection  to  trains  handling  freight  and 
passengers  at  stations,  a  signal  should  be  located  from  one  thousand  to 
twelve  hundred  feet  on  either  side  of  the  station;  this  will  allow  an 
approaching  train  to  advance,  and  often  avoid  making  a  stop  at  the 
signal  in  rear,  should  a  train  be  standing  within  station  limits. 

"The  length  of  block  must  be  determined  by  traffic  and  track  condi- 
tions. Where  the  traffic  is  not  very  heavy  and  the  road  bed  practically 
level  and  not  more  than  0.5  per  cent,  grade,  1-mile  blocks  are  considered 
very  good  practice.  If  traffic  is  congested  this  distance  should  be 
reduced  to  from  H  to  ^  mile.  On  approaching  ascending  grades  over 
0.5  per  cent.,  blocks  should  be  gradually  shortened  until  a  uniform  length 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK    201 

can  be  maintained;  this  should  be  done  in  order  to  avoid  any  unneces- 
sary stops  for  following  trains.  On  descending  grades,  blocks  can  be 
lengthened  to  conform  to  traffic  and  grade.  In  territory  comparatively 
level  and  where  traffic  is  not  congested,  IK-  to  2-mile  blocks  can  be 
successfully  operated. 

"No  location  of  a  signal  should  be  made  just  beyond  a  sag  or  apex, 
as  a  train  obliged  to  stop  at  such  a  signal  is  likely  to  break  in  two  in 
starting. 

"Before  making  a  final  survey  it  is  well  to  consult  with  the  engineering 
and  traffic  departments  relative  to  track  changes,  such  as  changing 
locations  of  crossovers  and  siding  switches,  and  in  some  cases  present 
sidings  may  be  eliminated,  thereby  saving  considerable  expense  if  these 
changes  can  be  made  before  signal  work  is  begun. 

"After  locations  have  been  made  and  considered  from  a  signaling 
standpoint,  the  transportation  department  should  be  consulted,  and 
the  ground  thoroughly  canvassed,  so  as  to  determine  definitely  that  the 
signals  as  located  can  be  successfully  operated  from  a  traffic  standpoint. 
It  is  also  a  good  plan  to  get  the  views  of  competent  enginemen  as  to 
locations,  and  ascertain  from  them  if  any  are  in  localities  liable  to  cause 
trouble. 

"In  some  foreign  countries,  the  practice  of  locating  signals  for  sight, 
is  to  use  a  full-sized  templet  of  a  mast  and  blade  and  send  out  a  locating 
party.  After  a  sight  has  been  selected,  the  templet  is  placed  in  position 
and  viewed  from  an  approaching  train.  If  not  seen  to  a  good  advantage, 
the  templet  is  moved  from  place  to  place  until  the  best  sight  is  obtained; 
this  accomplished  for  day  signals,  the  same  process  is  followed  at  night, 
except  that  a  light  is  placed  on  the  mast  instead  of  the  blade.  Very 
frequently,  in  making  both  night  and  day  tests,  it  is  found  that  the 
location  which  gives  the  best  sight  for  a  day  signal  may  not  answer  for  a 
night  signal,  which  necessitates  the  selection  of  a  new  location.  While 
this  method  may  at  first  glance  seem  to  be  unnecessary,  it  is  certainly 
well  worth  considering." 

132.  Two-position  Semaphore  Signaling.  —  Where  the  blocks 
are  rather  long,  the  home  and  distant  signal  arms  are  sometimes 

Train 


IP  IH  jp  JH  57?  SH 

FIG.  212.  —  One-arm  two-position  signals. 

mounted  on  separate  posts,  as  shown  in  Fig.  212.  These  signals 
give  only  two  indications,  stop  or  caution,  and  proceed.  The 
home  signal  stands  at  the  beginning  of  the  block  and  governs 
movements  into  the  block.  The  distant  signal,  serving  purely  a 


202 


RAILWAY  SIGNALING 


cautionary  function,  stands  from  2,000  to  4,000  ft.  in  the  rear  and 
simply  repeats  the  indications  of  the  home  signal.  The  train  has 
caused  the  home  signal  3H,  to  go  to  the  stop  position,  and  it,  in 
turn,  has  caused  distant  signal  3D  to  remain  in  the  caution  posi- 
tion. Both  signals  will  keep  these  positions  until  the  train 


y>^    . 


FIG.  213. — Two-arm  two-position  signals. 

passes  the  next  home  signal,  when  they  will  both  go  to  the  pro- 
ceed position  again. 

Where  the  blocks  are  shortened,  the  home  and  distant  signals 
are  usually  placed  on  one  mast,  as  shown  in  Fig.  213.  In  this 
case,  the  home  signal  governs  not  only  the  first  distant  signal  in 
the  rear,  but  also  the  one  on  its  own  mast.  In  the  case  of  a  four- 


/>  /*  \        ' 


/>/» . 

n  n  I ' 


/»HJ ' 


/>/r\- • 


FIG.  214. — Two-position  bracket  post  signals  on  a  four  track  line. 

track  line,  the  signals  are  frequently  mounted  on  the  bracket  type 
of  post  in  a  manner  such  as  is  indicated  in  Fig.  214.  The  inner 
signals  govern  track  No.  1  and  the  outer  ones  track  No.  2. 

133.  Three -position  Signaling. — The  three-position  signal  is  a 
step  in  advance  of  the  two-position,  for  it  combines  the  home  and 
distant  signal  in  one,  thereby  saving  about  half  of  the  posts, 


FIG.  215. — Three-position  lower  and  upper  quadrant  signals. 

motors,  and  lights.  This  reduces  not  only  the  rather  serious  first 
cost  in  the  matter  of  construction,  but  also  the  heavy  expense  of 
maintanence.  The  45-degree  position  signal  3,  Fig.  215,  indi- 
cates that  there  is  a  train  in  the  block  immediately  in  front  of  the 
one  it  governs,  and  warns  enginemen  to  be  prepared  to  stop  when 
they  reach  the  beginning  of  that  block. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK    203 

134.  Overlap  Systems.  —  As  a  measure  of  protection  an  over- 
lap system  was  devised  whereby  a  signal  did  not  go  to  clear  until 
the  train  had  advanced  a  certain  distance  beyond  the  next  home 
signal,  the  idea  being  to  keep  one  full  block  and  a  portion  of  an- 
other between  two  trains  going  in  the  same  direction.  In  Fig. 
216  a  train  in  section  A  of  block  3  holds  the  home  and  distant 

K  .......  Block  7-  .......  -*<--  .....  Block  2-  -------  ><-  .....  Blocks  --  -----  >i 

I  I  k-—  /?  -----    "       """"* 


w  w^ 

FIG.  216.  —  Partial  block  overlap. 

signals  at  the  beginning  of  block  2  in  the  stop  and  caution  posi- 
tions, but  when  it  passes  from  section  A  into  section  B  it  allows 
the  home  signal  to  go  to  the  proceed  position. 

This  system  is  often  criticised  on  the  ground  that  as  there  are 
times  when  there  are  two  home  signals  standing  in  the  stop  posi- 
tion between  one  train  and  another  one  following  it  as  closely  as 


FIG.  217. — Full  block  overlap. 

the  signals  will  permit,  the  enginemen  may  on  some  occasions  be 
inclined  to  pass  one  of  these  signals  at  high  speed. 

In  some  cases  where  the  blocks  are  short,  as  in  the  New  York 
Subway,  a  full  block  overlap  has  been  provided  in  order  to  secure 
additional  protection.  In  this  case  two  full  blocks  are  between 
two  trains  going  in  the  same  direction,  as  indicated  in  Fig.  217. 

135.  Absolute  and  Permissive  Signaling  on  Double  Track. — 
The  common  practice  in  double-track  automatic  block  signaling 
on  many  roads  is  for  a  train  to  stop  at  a  home  signal  that  shows  a 
stop  indication,  then  after  waiting  one  minute  proceed  at  such  a 
low  speed  as  to  be  able  to  stop  at  any  time.  The  stop  indication 
may  be  due  not  to  a  train  in  the  block,  but  to  a  break  in  the  rail 
or  to  an  obstruction  on  the  track  or  to  some  failure  of  the  signal 
apparatus;  and  if  there  should  not  be  some  method  of  procedure 
in  such  instances,  traffic  would  be  seriously  delayed.  Some  roads 
require  that  a  flagman  proceed  the  train  into  the  block  in  such 
cases  to  warn  it  of  the  danger.  This  plan  of  allowing  one  train 
to  follow  another  into  a  block  without  receiving  the  proper  indi- 
cation from  the  home  signal  to  do  so  is  called  permissive  signaling. 
Many  roads  distinguish  between  absolute  (stop  and  stay)  and 


204 


RAILWAY  SIGNALING 


permissive  (stop  and  proceed)  signals  by  making  the  blades  of  the 
absolute  home  signals  with  square  ends  and  those  of  the  permis- 
sive with  pointed  ends,  as  shown  in  Fig.  218  and  Fig.  219. 


FIG.  218.— Absolute  signal.     (Hall  Switch  and  Signal  Co.) 

The  night  indications  as  to  whether  a  signal  is  absolute  or 
permissive  is  shown  by  the  position  of  the  lamp,  called  a  marker, 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   205 

fastened  to  the  signal  post  some  distance  below  the  signal  lamp. 
A  marker  placed  directly  below  the  signal  lamp,  on  the  same  side 
of  the  post,  indicates  an  absolute  signal ;  and  on  the  opposite  side 


FIG.  219. — Permissive  signal.     (Hall  Switch  and  Signal  Co.) 

of  the  post,  a  permissive  signal.    A  marker  may  be  either  a  red  or  a 
yellow  light.    All  home  signals  at  interlocking  plants  are  absolute. 


206 


RAILWAY  SIGNALING 


136.  Three-block  Indication  Scheme. — Some  roads  have 
adopted  the  idea  of  using  two-arm  signals  for  giving  information 
to  trains  as  outlined  in  Fig.  220.  The  blades  are  made  with 
pointed  ends  and  operate  in  the  upper  quadrant.  In  the  case 
of  the  upper  blade,  the  signal  light  is  on  the  right-hand  of  side  of 


1.   Stop,  then  proceed. 


2.  Proceed  prepared  to  stop  at 
next  signal. 


3.  Proceed     prepared     to    pass 

next     signal     at     medium     O 
speed. 


4.  Proceed. 


j) 


J] 


FIG.  220. — Three-block  indication  scheme. 

the  post  and  in  the  case  of  the  lower  one,  on  the  left-hand  side  to 
act  as  a  permissive  marker.  This  combination  of  signals  affords 
a  much  wider  range  of  indications,  the  same  really  as  would  be 
displayed  by  a  four-position  signal,  and  is  used  to  give  indica- 
tions for  three  blocks  instead  of  two,  as  is  ordinarily  done  in 

n  n  ^>  n  ^>cq  <=3_o__ 

=*=?=    =f=  =^=^— =g 

FIG.  221. — Three-block  indications. 

practice.  A  train  in  block  A  will  cause  the  signal  to  display 
indications  as  shown  in  Fig.  221. 

137.  Numbering  Automatic  Signal  Posts. — All  automatic  sig- 
nal posts  should  be  numbered,  the  even  numbers  governing  trains 
going  in  one  direction  and  the  odd  numbers  those  in  the  opposite 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   207 

direction.  There  are  two  ways  of  designating  them,  one  is  to 
number  them  consecutively  through  the  mile,  and  the  other  to 
use  the  nearest  even  or  odd  tenth  of  mile  in  addition  to  the  mile- 
post  number.  By  the  first  method,  the  signals  running  in  one 
direction  between  mile  posts  264  and  265  would  be  2642,  2644, 
and  so  on  if  there  should  be  more  than  two;  and  in  the  other  direc- 
tion 2641,  2643,  and  so  on.  By  the  other  method  the  numbers 
would  be,  for  example,  2646  for  trains  in  one  direction  and  2649 
for  those  in  the  other,  depending  upon  the  particular  location 
that  the  signals  should  occupy  in  that  mile.  Branch  lines  may 
be  numbered  by  a  prefix  letter,  as  X2641  and  X2643.  Figure 
219  shows  the  method  of  numbering  main  line  posts.  Inter- 
locking signals  do  not  bear  numbers  except  the  distant  signal  used 
in  connection  with  three-position  automatic  block  signals. 


CHAPTER  XII 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK 
DIRECT-CURRENT  TRACK  CIRCUITS 

NORMAL  CLEAR  SIGNALS 

138.  Two-position  Signal  Circuits. — Figure  222  shows  the 
wiring  for  two-position  signals  on  double  track  where  the  home 
and  distant  signals  are  on  separate  posts.  The  home  signal  has  a 
very  simple  motor  control  circuit.  The  distant  signal  is  controlled 
by  the  front  contact  of  a  neutral  relay  for  a  train  in  its  immedi- 
ate section,  and  by  a  line  relay  and  circuit  breaker  operated  by 
the  home  signal  for  a  train  in  the  home  signal  section.  A  train  in 
block  C  will  deenergize  its  relay  and  cause  signal  H-3  to  go  to  the 
stop  position.  The  circuit  breaker  C-3  will  then  be  opened, 
breaking  the  circuit  to  S-3,  dropping  its  armature  and  allowing 


i 


P-3 


Common  Wi're-,, 


H-3 


Pis  font  Signal  Conj-wl  Wit 


FIG.  222. — Wiring  diagram  for  one-arm  two-position  signals. 

D-3  to  go  to  the  caution  position.  By  means  of  the  cut  section, 
signal  H-l  will  remain  in  the  stop  position  while  the  train  is  in 
section  B. 

Figure  223  shows  a  series  of  two  position  automatic  block 
signals  on  double  track  where  the  home  and  distant  signals  are 
on  the  same  post.  The  home  signal  governs  the  distant  signal  on 
the  same  post,  and  also  the  one  in  the  rear  by  means  of  circuit 
breakers.  A  train  in  block  C  shunts  its  track  relay  allowing  the 
home  and  distant  signals  5  to  go  to  the  stop  and  caution  positions. 
As  there  is  no  train  in  block  B,  home  signal  3  goes  to  the  proceed 
position,  but  distant  signal  3  remains  in  the  caution  position 

208 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK    209 

held  there  by  the  circuit  breaker  C-5.  The  circuit  that  energizes 
£-3,  the  control  relay  of  distant  signal  3,  is  from  battery,  through 
second  contact  of  track  relay  5,  circuit  breaker  C-5,  relay  S-3,  and 
common  return  to  battery.  When  this  circuit  is  broken  by  cir- 
cuit breaker  C-5,  the  relay  S-3  is  deenergized  breaking  the  front 


Common  Wire" 
FIG.  223. —  Two-arm  two-position  signal  circuits. 

contact  to  the  distant  signal  3.     Both  signals  in  block  A  are 
clear  because  the  circuit  breaker  C-3  is  closed. 

Figure  224  represents  a  wiring  diagram  for  two-arm  two-posi- 
tion signals  prepared  by  Committee  IV  of  the  Railway  Signal 
Association  and  printed  in  the  1910  issue  of  the  Proceedings.1 


H-  Home  Confm/  Pehy 
O  -  Distant      - 

FIG.  224. — R.    S.    A.    circuits    for    two-arm    two-position    signals. 
1076.4,  page  367,  Proceedings  1910.) 


(Plan    No. 


139.  Two-position  Polarized  Track  Circuits. — Figure  225 
shows  the  plan  for  polarized  track  circuits  for  two-position  signals 
where  the  home  and  distant  signals  are  on  separate  posts.  A 
train  in  block  C  will  drop  the  armature  and  break  the  circuit  to 
home  signal  3.  As  it  goes  from  the  clear  to  the  stop  position,  it 
shifts  the  pole  changer,  which  in  turn  changes  the  direction  of  the 
track  current  in  section  B.  This  repels  the  polarized  armature  P 

1  Page  367. 
14 


210 


RAILWAY  SIGNALING 


and  breaks  the  circuit  to  distant  signal  2  allowing  it  to  remain  in 
the  caution  position.  As  home  signal  1  is  controlled  only  by  a 
neutral  relay,  it  will  take  the  proceed  position.  This  plan  is  used 
only  where  the  traffic  is  light  and  the  blocks  are  long,  too  long  for 
a  distant  signal  to  be  a  full  block  from  its  governing  home  signal. 
Figure  226  shows  the  Union  plan  for  normal  clear  polarized 
track  circuits  and  two-position  signals  on  the  same  post.  In 
addition  to  the  pole-changer,  there  is  a  circuit  breaker  operated  by 


7-3 


FIG.  225. — Polarized  track  circuits  for  one-arm  two-position  signals. 

each  home  signal.  The  home  signal  is  connected  directly  in  cir- 
cuit with  the  battery  and  neutral  contact  of  the  relay.  The 
distant  signal  is  in  circuit  with  the  battery  and  neutral  contact  of 
the  neutral  relay  and  also  with  the  polarized  contact  of  the 
relay.  The  distant  signal  is  thus  controlled  entirely  by  the  home 
signal.  Whenever  a  train  enters  a  block  it  shunts  the  relay  and 
allows  the  home  signal  to  go  to  stop,  thereby  breaking  the 
circuit  to  the  distant  signal  on  the  same  post  setting  it  to  caution. 


FIG.  226. — Polarized  track  circuits  for  two-arm  two-position  signals. 


When  the  home  signal  is  horizontal,  it  manipulates  the  pole- 
changer  so  as  to  send  the  current  in  one  direction;  when  it  is  in 
the  proceed  position  it  causes  the  current  to  flow  in  the  opposite 
direction.  When  the  home  signal  goes  to  the  proceed  position 
the  circuit  is  made  through  the  polarized  armature  in  the  rear 
and  the  distant  signal  there  goes  to  clear. 

In  the  sketch,  the  train  is  deenergizing  the  first  track  relay  in 
the  rear  and  holding  the  signal  in  the  stop  position.  In  order  that 
the  home  signal  may  not  momentarily  tend  to  drop  the  stop 
position  while  the  pole-changer  breaks  the  track  circuit,  shifting 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   211 


from  one  contact  to  the  other,  a  slow  releasing  magnet  is  fre- 
quently employed. 

Figure  227  represents  typical  circuits  for  two-arm  two-position 
polarized  track  circuits,  while  Fig.-228  represents  typical  circuits 
for  two-arm  two- position  polarized  line  circuits.1 


FIG.  227. — R.  S.  A.  two-arm  two-position  signals,  polarized  track  circuits. 
(Plan  No.  1Q77A,  Page  368,  Proceedings  1910.) 

140.  Three-position  Signal  Circuits. — A  sketch  of  the  General 
Railway  Signal  wiring  plan  for  three-position  signals  is  shown 
in  Fig.  229.  The  45-degree  position  of  signal  1  is  controlled  by 
a  circuit  through  its  local  battery,  third  and  fourth  contacts  of 
the  track  relay,  and  the  common  return.  The  90-degree  position 
is  controlled  by  the  circuit  breaker  and  the  battery  of  the  signal 
in  advance.  If  the  block  that  is  governed  by  signal  3  is  occupied 


i 


FIG.  228. — R.  S.  A.  diagram  for  two-arm  two-position  signals.     Polarized  line 
circuits.     (Plan  1078A,  page  369,  Proceedings  1910.) 

by  a  train,  its  relay  is  deenergized  and  signal  3  goes  to  the  stop 
position.  As  the  block  that  is  governed  by  signal  1  is  not  occup- 
ied, its  relay  becomes  energized  and  signal  1  goes  to  the  45-degree 
position.  As  the  tain  moves  one  block  to  the  right,  signal  3  goes  to 
the  45-degree  position  and  signal  1  goes  to  the  90-degree  position 
because  the  90-degree  relay  at  signal  1  becomes  energized  from 
the  battery  at  signal  3. 

1  Proceedings  Railway  Signal  Association,  pages  368  and  369,  Volume  1910. 


212 


RAILWAY  SIGNALING 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK    213 

141.  Three-position  Polarized  Track  Circuits.— Figure  230 
shows  the  Union  design  for 
a  three-position  signal  system 
operated  by  polarized  track 
circuits.  The  45-degree  po- 
sition is  controlled  by  the 
neutral  contacts  and  the  90- 
degree  position  by  the  polar- 
ized contacts. 

-» 

NORMAL  DANGER  SIGNALS 


142.  Two-position  Signal 
Circuits.  —  Normal  danger 
signals  are  those  that  stand 
normally  at  stop  when  the 
track  is  not  occupied,  but 
which  go  to  the  proceed 
position  upon  the  approach 
of  a  train.  They  assume  the 
stop  position  again  as  soon 
as  the  train  enters  the  block 
they  govern. 

Figur^  231  is  plan  1,079 A 
printed  in  the  1910  issue  of 
the  Proceedings  of  the  Rail- 
way Signal  Association,  with 
some  additional  lettering  to 
aid  in  explanation,  and  rep- 
resents a  two-arm  two-posi- 
tion normal  danger  system. 
When  a  train  enters  the  last 
section  of  block  A,  distant 
signal  3  and  home  signal  5  go 
to  clear  provided  there  is  no 
train  in  either  block  B  or  C. 
The  circuit  for  clearing  these 
two  signals  is  battery  at  signal 
7,  second  contact  of  relay  C-5, 
first  contact  relay  T-5,  relay 
H,  relay  A,  middle  circuit 
breaker  at  signal  3  closed  by  home  signal  3  cleared,  relay  D,  back 


214  RAILWAY  SIGNALING 

side  fourth  contact  on  relay  C-l,  and  common  return  to  battery 
at  signal  7. 

When  the  train  enters  block  B,  the  home  signal  3  goes  to 
stop  because  the  circuit  is  broken  by  the  track  relay.  This,  in 
turn,  opens  the  middle  circuit  breaker  operated  by  home  signal  3 
and  allows  the  distant  signal  3  to  go  to  caution.  Home  signal  5 
remains  at  clear,  for  the  current  has  another  route  through  the 
back  side  of  the  third  contact  of  relay  C-3  and  through  the 
resistance  to  the  common  wire.  Home  signal  7  and  distant 
signal  5  go  to  clear  when  the  train  enters  the  last  section  of 
block  B. 

The  function  of  relay  A  is  to  allow  relay  H  to  pick  up  first, 
clearing  home  signal  5  before  relay  D  can  pick  up  to  clear  the 
distant  arm  of  signal  3. 

SWITCH,  CURVE,  AND  SIDING  PROTECTION 

143.  Switch  Indicators. — When  the  movements  of  a  train  are 
controlled  by  automatic  block  signals,  switch  indicators,  as  shown 
in  Fig.  167,  are  usually  provided  at  the  switches,  especially  those 
in  outlying  districts.  The  indications  may  be  either  visible  or 
audible,  and  are  to  inform  a  switchman  whether  or  not  a  train  is 
approaching,  so  that  he  can  be  governed  intelligently  concerning 
the  opening  of  the  switch.  Visible  signals  are  either  miniature  discs 
or  semaphore  arms  actuated  by  electro-magnets  energized  by  line 
wire  circuits  that  extend  through  at  least  two  full  blocks  in  the 
rear  of  the  switch.  These  wires  are  connected  through  the  nor- 
mally closed  contacts  of  all  the  track  relays  or  home  signal  arms 
in  those  two  blocks  so  that  the  approach  of  a  train  will  break  the 
circuit  and  allow  the  indicator  to  come  to  stop.  Thus  the 
switchmen  receive  a  warning  that  a  train  is  immediately  approach- 
ing and  will  not  open  the  switch  until  the  train  has  passed.  The 
indicator  is  enclosed  in  an  iron  case  with  a  glass  front,  and  is 
placed  in  such  a  position  near  the  switch  stand  that  it  can  be 
easily  seen  by  switchmen. 

The  audible  warning  is  given  by  a  bell  placed  in  the  immediate 
vicinity  of  the  switch.  The  wiring  for  the  bells  is  practically  the 
same  as  it  is  for  the  visible  indicators.  In  either  case  the  wiring 
should  extend  back  far  enough  so  that  the  warning  should  occur, 
at  least,  by  the  time  the  train  approaches  the  distant  signal  con- 
trolled by  the  first  home  signal  in  the  rear  of  the  switch. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK    215 


144.  Switch  Box.  —  Located  at  each  switch  in  a  track  with 
automatic  block  signals  is  a  switch  circuit  controller,  Fig.  232,  so 


FIG.  232. — Switch  circuit  controller. 


connected  to  the  switch  points  by  a  rod  that  when  the  switch  is 
open  the  circuit  through  the  switch  box  is  closed.     They  are 


FIG.  233. — R.  S.  A.  circuits  for  protection  of  facing  switches.     (Plan  1312.) 

generally  made  with  four  contacts  not  all  of  which  may  be  used  at 
one  time.     The  switch  box  is  usually  arranged  to  shunt  the  track 


m 


Add.  for  Normal  fanger—  —  —  — 
Omit  »       »  »        iiiii- 

FIG.  234. — R.  S.  A.  design  for  protecting  obscure  curves  and  switches. 
(Plan  1075A,  page  366,  Proceedings  1910.) 

circuit,  although  sometimes  it  is  placed  in  the  circuit  that  con- 
trols, at  least,  the  first  home  signal  in  the  rear,  so  that  when  the 
switch  is  open  the  home  signal  will  give  the  stop  indication. 


216 


RAILWAY  SIGNALING 


145.  Signals  for  .Outlying  Switches  and  Obscure  Curves. — 

Where  the  automatic  block  system  is  not  in  use,  signals  are  some- 
times installed  to  protect  trains  at  outlying  facing  point  switches 
and  on  abscure  curves  where  the  view  is  somewhat  obstructed. 
In  the  case  of  the  switch,  the  signal  may  be  mechanically  operated 
by  wires  connected  directly  to  the  switch  mechanism  or  it  may  be 
operated  by  power,  the  Railway  Signal  Association  diagram  of 


Add  for  Harm  a  I  Danger 
Omit  n        »  » 


I 
I 

I 

-J 

FIG.  235. — R.  S.  A.  normal  clear  circuits  for  trailing  switch  and  curve  protection. 
Traffic  in  one  direction.     (Plan  1074^4.,  page  365,  Proceedings  1910.) 

which  is  shown  in  Fig.  233.  In  this  plan  there  are  two  block 
sections  with  independent  track  circuits,  either  one  of  which  when 
occupied  by  a  train  will  set  the  switch  indicator  to  stop. 
When  the  switch  is  opened,  or  when  the  block  in  which  it  is  located 
is  occupied  by  a  train,  the  signal  will  be  placed  in  the  stop  posi- 
tion automatically.  Figure  234  represents  the  Railway  Signal 
Association  circuit  plan  for  protecting  obscure  curves  and  sidings. 


CHAPTER  XIII 
AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK 

ALTERNATING  CURRENT 

146.  Introductory. — Alternating  current  is  used  for  signaling 
purposes  on  electric  lines  whether  the  propulsion  current  be 
direct  current  or  alternating.  In  the  case  of  direct-current  pro- 
pulsion any  commercial  frequency  of  cycles  may  be  used  for  the 
signal  current,  but  in  the  case  where  alternating-current  propul- 
sion is  used,  the  two  cycles  must  be  different.  The  signaling 
current  is  entirely  independent  of  the  propulsion  current.  It  is 
obtained  from  a  substation,  is  carried  along  the  right-of-way  on  a 
separate  set  of  poles,  and  has  its  voltage  stepped  down  by  means 
of  transformers.  As  it  is  used  for  operating  both  track  circuits  and 
signals,  it  has  the  advantage  of  eliminating  the  expense  of  bat- 
teries, and  of  battery  wells  and  battery  chutes.  It  serves  to 
avoid,  also,  the  difficulties  that  arise  from  foreign  currents 
carried  by  the  rails.  To  a  certain  extent  it  eliminates  the  cut 
section  so  commonly  used  in  direct-current  signaling,  for  in 
many  cases  the  track  circuit  can  be  made  as  long  as  the  clock. 
The  current  can  be  used,  also,  for  lighting  the  signals,  switches, 
stations  and  other  buildings  along  the  line.  Furthermore,  there 
is  not  so  much  chance  of  signal  failure  in  unfavorable  weather 
because  of  the  greater  amount  of  power  available  for  such  pur- 
poses. It  does  require,  however,  a  constant  generation  of  current 
and  the  additional  set  of  poles  for  transmission.  Should  the 
transmission  line  fail  at  any  place,  that  part  of  the  system  would 
go  out  of  service  that  should  lie  beyond  the  point  of  failure  unless 
power  should  be  supplied  from  some  other  source.  The  first  cost 
of  installing  alternating-current  equipment  is  generally  heavier 
than  that  for  direct  current. 

On  account  of  fewer  complications  in  line  construction,  single- 
phase  transmission  is  generally  used  in  preference  to  three-phase 
where  the  current  is  not  too  heavy  or  the  length  of  line  too  great. 
Voltages  of  1,100,  2,200, 3,300,  and  4,400  are  being  transmitted  for 
signaling  purposes.  The  higher  the  voltage  the  less  copper 
necessary  for  the  transmission  service;  but  at  the  same  time,  the 

217 


218 


RAILWAY  SIGNALING 


high-voltage  current  requires  more  expensive  auxiliary  equip- 
ment, such  as  transformers  and  lightning  arresters.  Single- 
phase  current  also  eliminates  the  difficulties  that  arise  from  an 
unequal  distribution  of  the  current  in  the  three  wires  in  the  case  of 
three-phase  transmission.1 

SINGLE-RAIL  RETURN2 

147.  Direct-current  Propulsion. — There  are  two  systems  in 
practice  where  electricity  is  used  for  propulsion  and  where  alter- 
nating current  is  used  for  signaling,  the  single-rail  return  and  the 
double-rail  return.  The  single-rail  return  can  be  used  only  where 
the  return  propulsion  current  is  light  enough  to  be  carried  by  one 
rail  and  where  it  is  not  necessary  to  guard  against  broken  rails, 
as  in  yards  where  train  movements  are  slow.  The  double-rail 


FIG.  236. — Single-rail  return  system. 

return  requires  more  track  equipment,  which  makes  that  system 
less  desirable  in  yards  and  busy  terminals.  In  the  single-rail 
return  system  one  rail  is  divided  into  blocks,  as  shown  in  Fig.  236, 
to  operate  the  signal,  and  the  other  is  left  intact  to  act  as  a  return 
for  the  propulsion  current.  It  also  serves  to  complete  the  track 
circuit. 

In  practice  when  the  block  is  not  occupied  or  when  the  train 
is  in  the  middle  of  the  block  almost  all  of  the  return  propulsion 
current  flows  through  the  one  rail  and  there  is  a  drop  in  the  poten- 
tial between  the  two  rails  at  each  end  of  the  block  depending  upon 
the  amount  of  resistance  inserted  at  each  place,  the  resistance  of 

1  Page  90,  Proceedings  Railway  Signal  Association,  1917. 

2  From  a  paper  by  W.  K.  HOWE,  Proceedings,  Railway  Signal  Association, 
Page  130,  1909. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   219 


the  rail  and  the  amount  of  propulsion  current  in  the  continuous 
rail.  When  the  train  is  entering  or  leaving  the  block,  there  is  a 
tendency  for  a  greater  portion  of  the  propulsion  current  to  go 
through  the  block  rail.  In  the  first  case,  when  the  block  is  not 
occupied,  there  would  be  a  tendency  for  some  of  the  current  to 
flow  from  the  return  rail  through  the  relay  at  one  end  of  the  block 
and  through  the  block  rail  to  the  secondary  coils  of  the  track 
transformer  at  the  other  end  and  to  the  return  rail  again.  In 
the  second  case  there  would  be  the  tendency  for  a  greater  portion 
of  the  propulsion  current  to  go  through  the  track  transformer 
when  the  train  enters  the  block  and  to  flow  through  the  relay 
when  it  leaves  the  block.  This  would  magnetize  the  iron  of  the 


FIG.  237. — Cast  iron  resistance  grid. 

relay  and  transformers  to  such  an  extent  as  to  interfere  with  the 
operation  of  the  signal  current.  To  eliminate  this  element  of 
interference,  two  non-inductive  resistances  R  and  Ri  are  inserted 
in  the  track  circuit,  the  one  at  the  relay  and  the  other  at  the 
track  transformer.  Where  the  blocks  are  only  200  or  300  ft. 
long  and  the  current  is  comparatively  light,  tube  resistances  are 
sufficient,  but  where  the  blocks  are  800  or  900  ft.  long  and  the 
current  correspondingly  heavy,  cast-iron  grids,  such  as  shown  in 
Fig.  237,  are  employed.  These  resistances  are  high  and  the 
voltage  of  the  track  current  will  need  to  be  proportionally  high 
to  drive  the  current  through  them.  This  will  lead  to  a  consider- 
able waste  of  current  by  leakage  between  the  two  rails  with  a 
corresponding  drop  in  voltage  varying  with  the  initial  voltage, 
length  of  block,  and  the  ballast  and  track  conditions.  This 


220 


RAILWAY  SIGNALING 


type  of  construction  can  be  used  economically  only  in  cases  where 
the  difference  in  the  pressure  of  the  propulsion  current  in  the  con- 
tinuous rail  at  the  two  ends  of  the  block  does  not  exceed  15  volts. 
Such  a  drop  would  be  equivalent  to  that  from  a  current  of  1,500 
amp.  in  1,000  ft.  of  ordinary  80-lb.  rail.  If  the  difference  exceeds 
this  amount  R  and  Ri  would  have  to  be  increased  with  a  corre- 
sponding increase  in  initial  voltage  and  greater  loss  of  alternating 
current. 

If  this  resistance  is  not  sufficient,  a  low  ohmic  resistance  impe- 
dance coil,  x,  is  placed  in  multiple  with  the  relay  and  a  cast- 
iron  grid  for  a  non-inductive  resistance  in  series  with  both  the 
relay  and  the  track  transformer  as  illustrated  in  Fig.  238.  The 


n 

FIG.  238. — Single-rail  return.     Impedance  coil  shunting  relay. 

impedance  coil  shown  in  Fig.  239  offers  a  high  resistance  to  the 
alternating  current,  but  a  low  resistance  to  the  propulsion  direct 
current.  The  shunting  of  the  relay  and  the  peculiar  construction 
of  the  track  transformer  allow  a  much  heavier  propulsion  current 
to  flow  without  injuring  the  relay  and  the  track  transformer. 
This  permits  of  greater  drop  of  voltage  of  the  propulsion  current 
in  the  continuous  rail,  allowing  longer  blocks  and  heavier  cur- 
rents than  is  possible  to  use  with  the  other  type. 

As  a  further  measure  of  resistance  to  the  flow  of  the  direct 
current  through  the  track  circuit  line,  an  air  gap  is  provided  in 
both  the  impedance  coil  and  the  track  transformer.  The  re- 
sistance in  the  track  transformer  circuit  tends  to  reduce  the  flow 
of  alternating  current  when  the  block  is  occupied  by  a  train. 
Fuses  are  provided  to  protect  the  equipment  should  a  short 
circuit  occur  between  the  block  and  continuous  rails  as  when  tools 
are  laid  across  the  track.  In  double  track,  the  two  continuous 
rails  can  be  cross  bonded  as  frequently  as  seems  desirable. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   221 


The  plan  indicated  in  Fig.  238  has  the  advantage  that  since 
only  a  small  amount  of  current  flows  through  the  relay  and  trans- 
former, the  wires  permit  the  relay  and  transformer  to  be  located 
in  the  tower  at  interlocking  plants  without  very  much  additional 
expense.  This  avoids  the  necessity  of  having  a  secondary  relay 
in  those  cases  where  the  track  circuit  must  be  repeated  into  the 
tower  and  allows  one  large  transformer  to  serve  all  track  relays 

and  track  circuits.     Since  the  resist-   

ance  of  R  and  R\  are  relatively  small, 
their  cost  is  proportionally  decreased, 
and  their  size  permits  of  their  being 
mounted  in  a  comparatively  small 
space. 

On  account  of  the  difference  in 
potential  between  the  two  ends  of 
the  block,  the  single-rail  return  finds 
its  best  service  in  short  blocks,  as  for 
example,  the  New  York  Subway, 
where  the  average  length  is  a  little 
more  than  800  ft.  In  the  operation 
of  this  Subway,  the  transmission 
lines  carry  a  60-cycle  current  of  500 
volts  potential.  The  current  is  stepped 
to  50  volts  for  signal  lights  and  to  10  volts  for  the  track  circuit. 
The  non-inductive  resistance  at  each  end  of  the  block  accounts 
for  about  2  or  2V£  volts  so  that  the  current  at  the  single-phase 
relay  is  practically  5  volts.  The  grid  resistance  between  the 
transformer  and  the  block  rail  and  between  the  relay  and  the 
block  rail  is  1  ohm. 

The  single-rail  system  is  suitable,  also,  for  short  blocks  through 
interlocking  plants  where  the  track  layouts  are  somewhat  com- 
plicated. As  only  one  rail  is  divided,  the  track  circuit  instal- 
lation becomes  much  simpler  requiring  less  expenditure  in  the 
first  cost  of  construction  and  less  expense  for  maintenance. 

148.  Impedance  Coil. — Direct  current  will  have  no  effect  on  the 
alternating-current  relay  except  to  further  magnetize  the  core. 
.Up  to  a  certain  point  this  is  not  detrimental,  and  beyond  that  it 
is  taken  care  of  by  inserting  the  impedance  coil,  Fig.  239,  in 
multiple  with  the  relay.  The  iron  core  of  the  impedance  coil  is 
made  with  an  air  gap  so  that  the  extra  magnetization  does  not  take 
effect  until  the  direct  current  reaches  a  value  of  20  amps. 


FIG.  239. — Impedance  coil. 


222 


RAILWAY  SIGNALING 


149.  Track  Transformer.— The  track  transformer,  shown  in 
Fig.  240,  is  of  the  open  magnetic  circuit  type  designed  for  use 
on  roads  having  direct-current  propulsion  with  single-rail  return. 
Most  of  these  transformers  have  secondary  coils  for  supplying 
both  track  and  light  circuits. 


PLAN  VIEW 

COVER  REMOVED 


SECTIONAL  FRONT  VIEW  SIDE  VIEW 

CASE  SECTIONED 

FIG.  240. — Transformer.     Open  magnetic  circuit  type. 


DOUBLE-RAIL  RETURN 

150.  Direct-current  Propulsion.1 — Whenever  the  propulsion 
current  is  heavy  enough  to  require  both  rails  to  carry  the  return 
current,  the  double-rail  return  system  is  employed  as  illustrated  in 
Figs.  241  to  243,  inclusive.  Either  direct  or  alternating  current 
may  be  utilized  for  propulsion.  In  order  that  there  may  be  no 
conflict  between  the  direct  current  used  for  propulsion  and  the 
alternating  current  used  for  signaling,  impedance  bonds  either 
with  or  without  iron  cores  are  installed  to  connect  the  two  rails 

1  Proceedings,  Railway  Signal  Association,  Page  130,  1909. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   223 


at  each  end  of  the  block.  Those  with  iron  cores  are  shown  in 
Figs.  241  and  242,  while  whose  without  the  core  are  represented 
by  Fig.  243.  These  bonds  have  practically  no  effect  on  the  direct 
current,  but  offer  an  impedance  to  the  flow  of  the  alternating 
current.  Thus  the  track  is  continuous  for  the  propulsion 


FIG.  241. — Double-rail  return  system. 


current,  but  divided  into  blocks  for  the  signaling  current.  The 
signaling  current  may  be  fed  into  the  end  of  the  block  or  into 
the  center  of  the  block,  in  which  case  they  are  known  as  "end-fed" 
or  "center-fed."  Figures  241  and  243  are  end  fed,  while  Fig.  242 
is  center-fed. 


3 

? 

JT~ 

+ 

"1. 

§ 

c 

n 

FIG.  242.— Double-rail  return.     Center-fed. 

The  iron  impedance  bond,  Fig.  244,  is  made  of  six  or  eight 
turns  of  large  carrying  capacity  strap  copper,  wound  around  a 
laminated  core  of  iron,  but  insulated  from  the  core.  The  coils  of 
two  adjacent  blocks  are  connected  by  a  copper  cable  tapped  into 
the  center  of  each  coil  as  shown  in  Fig.  241.  The  coils  and  core 


224 


RAILWAY  SIGNALING 


n 

FIG.  243. — Double-rail  return.     Ironless  impedance  bonds. 


PLAN  VIEW  COVER  REMOVED 


AfHOU 


SIDE  VIEW  IN  SECTION 

SECTION  A-B 

FIG.  244.— Impedance  bond. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   225 


are  enclosed  in  an  iron  box  placed  usually  between  the  rails  of  the 
track. 

As  the  propulsion  current  flows  into  the  center  of  the  imped- 
ance bond,  and  through  the  two  halves  of  the  coil  in  the 
opposite  direction,  there  should  be,  theoretically,  the  same  amount 
of  return  current  in  each  rail  with  no  magnetic  effect  on  the  cores 
of  the  bonds.  With  the  same  return  current  in  each  rail,  there 
should  be  no  difference  in  potential  between  the  two  rails  at 
either  end  of  the  block  and  no  direct  current  should  flow  through 
the  relay  and  track  transformer;  consequently,  there  would  need 


FIG.  245. — Impedance  bonds  in  place. 

to  be  no  resistance  grids  nor  shunt  coil  to  protect  them.  In 
practice,  however,  on  account  of  faulty  bonds  at  rail  joints,  the 
same  amount  of  return  current  does  not  flow  through  the  two 
rails  and  the  two  halves  of  the  coil;  and  this  tends  to  magnetize 
or  unbalance  the  core,  reduce  the  resistance  to  alternating 
current,  and  divert  more  of  the  signal  current  from  the  relay. 
To  eliminate  this  shunting  of  the  relay,  the  impedance  bonds  are 
made  with  an  air  gap  in  the  core  so  as  to  reduce  the  magnetizing 
effect  and  the  consequent  unbalancing.  The  track  transformer 
is  not,  however,  provided  with  an  air  gap  as  it  was  in  the  single- 

15 


226  RAILWAY  SIGNALING 

rail  return  type.  It  is  best  in  designing  these  bonds  to  provide 
for  an  unbalancing  of  20  per  cent.;  that  is,  to  figure  that  the  dif- 
ference in  the  amount  of  the  current  between  the  two  rails  may  be 
as  much  as  20  per  cent,  of  the  total  carried  by  both. 

The  coils  used  in  the  Hudson  Tubes  are  750,000  circular  mil 
copper  with  a  resistance  of  0.00073  ohm  per  pair  for  the  direct 
current.  They  have  a  continuous-current  capacity  of  approxi- 
mately 1,300  amp.  per  track  and  an  unbalancing  capacity  of 
approximately  500  amp.  Those  used  on  the  New  York  Central 
are  1,250,000  circular  mil  copper  with  a  resistance  of  0.00014  ohm 
per  pair  for  the  direct  current.  They  have  a  continuous-current 
capacity  of  approximately  4,000  amp.  per  track  and  an  unbal- 
ancing capacity  of  approximately  1,000  amp.  The  bonds  used 
in  the  Hudson  Tubes  weigh  about  950  Ib.  and  on  the  New 'York 
Central  about  1,500  Ib.  per  pair  when  filled  with  oil. 

When  the  alternating  current  flows  through  an  impedance 
bond,  it  encounters  a  much  higher  resistance  than  direct  current 
does.  For  example,  in  the  case  of  the  New  York  Central, 
while  the  ohmic  resistance  of  the  copper  to  the  propulsion  current 
is  only  0.00028  ohm  between  the  two  rails  at  both  ends,  the 
resistance  to  the  25-cycle  signal  current  is  0.06  ohm,  or  approxi- 
mately 200  times  greater,  and  is  explained  in  the  following  manner: 

A  current  through  a  coil,  especially  that  of  an  electro-magnet, 
produces  a  magnetic  fielcl  that  sets  up  a  counter  electro-motive 
force  in  the  coil  itself.  This  opposes  the  voltage  and  interferes 
with  the  building  up  of  the  current.  In  the  case  of  alternating 
current,  there  is  no  chance  to  build  up  a  strong  magnetic  field 
because  of  such  frequent  change  in  direction  of  the  current.  The 
greater  the  number  of  turns  in  the  coil  and  the  greater  the  amount 
of  iron  in  the  core,  the  greater  is  this  resistance  of  impedance. 
The  impedance  increases  also  with  cycle  frequency.  A  bond 
that  would  have  an  impedance  of  0.06  ohm  at  25  cycles  would 
have  an  impedance  of  0.14  ohm  at  60  cycles. 

End-fed  track  circuits  may  be  installed  in  blocks  up  to  2,000 
ft.  long  where  100-lb.  rails  are  used  in  the  track  with  0.06  ohm 
impedance  bonds  connecting  them.  Beyond  this  length  center-fed 
tracks  circuits  may  be  employed  with  the  same  rail  and  bonds  in 
blocks  up  to  6,000  ft.,  if  cross-bonding  conditions  will  permit. 
The  center-fed  type  requires  no  resistance  at  the  track  trans- 
former, while  the  end-fed  frequently  does.  It  does  require, 
however,  an  extra  relay  with  its  transformer  at  each  end  of  the 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   227 

block  and  a  great  deal  of  extra  wiring  to  connect  the  signals  with 
the  two  sets  of  relays.  This  type  of  bonding  and  signaling 
finds  its  best  service  where  traffic  is  heavy  requiring  more  return 
current  than  one  rail  can  carry  and  where  the  blocks  are  average 
length  or  longer.  Cross  bonding  between  tracks  can  be 
done  only  at  the  ends  of  the  blocks.  On  account  of  the  size 
of  the  housing  for  the  bonds  and  the  size  of  the  cables,  the  equip- 
ment is  not  very  suitable  for  terminals  and  other  complicated 
track  construction. 

The  ironless  impedance  bonds,  shown  in  Fig.  243,  consist 
simply  of  a  much  greater  number  of  turns  of  heavy  copper  wire 
without  the  enclosed  iron  core.  The  cost  of  the  copper  becomes 
such  a  factor  in  this  case  that  it  is  practical  to  use  this  system 
only  where  the  current  is  light  enough  to  permit  a  smaller  wire. 
Resistance  is  inserted  in  the  track  circuit  at  the  transformer, 
and  the  bonds  are  connected  between  the  rails  as  in  the  previous 
cases.  Where  the  wire  connecting  the  two  bonds  at  the  ends  of 
adjacent  blocks  tap  each  coil  in  the  middle,  full  protection  is 
afforded  against  broken  rails.  In  Fig.  243  the  bonds  are  con- 
nected across  as  usual,  but  the  relay  itself  is  on  a  secondary 
winding.  This  prevents  the  heavy  direct  current  from  flowing 
through  the  relay.  On  account  of  there  being  no  iron  core,  there 
is  no  unbalancing  effect  in  this  system  to  interfere  with  the 
impedance.  End-fed  circuits  may  be  1J^  miles  long  and  center- 
fed  3  miles  long. 

151.  Alternating-current    Propulsion.— The    same    type    of 
construction  is  used  as  for  direct-current  propulsion,  but  on 
account  of  the  high  voltage  of  the  propulsion  current  the  amper- 
age is  low  and  consequently  can  be  carried  by  lighter  and  cheaper 
impedance  bonds.     The  track  relays  are  somewhat  different  and 
the  impedance  bonds  are  made  without  air  gaps.     In  order  that 
the  relay  may  not  respond  to  both  currents,  the  cycle  frequency 
of  the  signal  current  must  be  different  from  that  of  the  propulsion 
current.     If  the  latter  should  be  25  cycles,  the  former  should  be 
60,  for  these  are  the  values  commonly  found  in  practice. 

ALTERNATING-CURRENT  SIGNALING  ON  STEAM  ROADS 

152.  General. — On  account  of  the  difficulties  experienced  with 
foreign   currents   interfering   with   track   circuits   operated   by 
batteries,  it  has  seemed  best  in  many  cases  to  employ  alternating 
current  for  signaling  purposes  on  steam  roads.     This  interference 


228  RAILWAY  SIGNALING 

comes  in  many  cases  from  electric  railway  lines  that  run  parallel 
to  adjacent  steam  tracks.  The  signal  current  may  be  used  also 
to  operate  signal  motors  and  to  give  night  indications  in  signals 
and  switches.  The  current  for  the  track  circuit  for  operating 
the  signal  motor  and  for  lighting  switch  and  signal  lamps  is  all 
taken  from  the  signal  mains  and  stepped  down  by  transformers 
as  before.  Both  rails  are  divided  into  blocks,  but  since  there  is 
no  return  propulsion  current,  no  impedance  bonds  are  necessary. 
A  continuous  track  circuit  is  used  the  entire  length  of  its  blocks, 
thus  eliminating  the  cut  section  so  often  necessary  with  direct- 
current  signaling.  Blocks  as  much  as  2  miles  in  length  may  be 
operated  in  this  manner. 

TRANSFORMERS 

153.  General. — The  closed  magnetic  circuit  type  of  trans- 
former, shown  in  Fig.  246,  is  designed  for  use  on  roads  having 
direct-  or  alternating-current  propulsion  with  double-rail  return. 
It  is  also  used  on  steam  roads  having  alternating-current 
signaling. 

The  following  suggestions  from  the  1917  Proceedings  of  the 
Railway  Signal  Association  are  helpful  in  making  connections 
for  a  series  of  transformers. 

"Care  should  be  taken  to  connect  all  transformer  primary  leads  in  the 
same  manner,  i.e.,  take  one  transmission  line  wire  and  call  it  A.  Con- 
nect the  right-hand  lead  of  all  transformers  as  viewed  when  looking  at 
front  of  same  to  this  wire.  This  gives  the  same  instantaneous  polarity 
for  the  corresponding  secondary  lead  of  all  transformers.  This  is  very 
desirable  in  order  to  obtain  proper  polarity  on  track  circuits  and  also 
on  line  circuits  when  using  three-position  line  relays. 

"In  order  to  insure  a  uniform  polarity  scheme,  the  installation  should 
be  made  as  follows: 

"First. — If  possible,  locate  all  transformers  on  the  same  side  of  the 
transmission  line  pole  and  connect  the  primary  leads  to  corresponding 
wires.  Care  should  be  taken  to  avoid  error  due  to  transposition  of  the 
transmission  line  wires. 

"Second. — If  necessary  to  put  a  transformer  on  the  opposite  side  of 
the  pole,  interchange  the  connections  of  the  primary  leads  to  the  line 
wires;  this  should  also  be  done  if  the  transformer  is  on  the  standard 
side  of  the  pole,  but  a  transposition  of  line  wires  has  been  made. 

"Primary  leads  may  be  interchanged  at  the  terminal  board  inside 
the  transformer,  if  they  are  long  enough.  This  is  not  considered 
entirely  desirable,  however,  as  there  is  not  much  space  to  cross  these 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   229 

high-tension  leads  inside  the  transformer,  hence  this  is  usually  done  by 
cleating  the  leads  to  the  underside  of  the  cross  arm  with  porcelain 
cleats  and  using  wire  insulated  for  high  voltage  for  the  taps  from  the 
transformer  to  the  line. 

"Where  there  is  only  one  secondary  winding,  it  is  not  absolutely 
necessary  to  interchange  the  primary  leads  as  this  may  be  done  with  the 
secondary  leads.  It  is  preferable,  however,  to  interchange  the  primary 


PLAN  VIEW  COVER  REMOVED 


FRONT  VIEW 

CASE  SECTIONED 

THRO*  A-B 


SIDE  VIEW 

CASE  SECTIONED 

THRO'  C-D 


FIG.  246. — Transformer.     Closed  magnetic  circuit  €ype. 

leads  and  have  all  corresponding  secondary  leads  of  the  same  polarity. 
This  insures  a  uniform  scheme  in  connecting  and  tagging  all  wires. 

"In  carrying  out  the  polarity  scheme,  care  must  also  be  taken  when 
energy  is  obtained  from  several  sub-stations  to  insure  that  corresponding 
line  wires  from  each  sub-station  have  the  same  polarity.  This  is  ob- 
tained by  connecting  each  primary  lead  of  the  signal  power  transformers 
to  the  corresponding  bus  in  each  substation  and  taking  corresponding 
line  wires  from  corresponding  secondary  terminals  of  the  power 
transformers." 


230 


RAILWAY  SIGNALING 


ALTERNATING-CURRENT  RELAYS 

154.  General. — Alternating-current  relays  may  be  the  single- 
phase  induction  type  energized  by  the  track  circuit  only;  or  they 
may  be  two-winding,  either  the  induction  motor  type  or  the  poly- 
phase type,  one  winding  of  which  is  energized  by  the  transmission 
line  and  the  other  by  the  track  circuit.     The  single  winding  is 
simpler  in  construction,  but  requires  more  energy  to  actuate  it 
than  the  two-winding.     It  would  require  a  high  voltage  to  send 
a  current  through  a  block  2  miles  long  and  operate  a  single-phase 
relay  successfully,  so  high  that  most  of  it  would  be  lost  by  leakage. 
In  the  case  of  the  two-winding  relay,  however,  the  transmission 
winding,  which  is  located  practically  at  the  relay,  is  usually  55  to 
110  volts  and  furnishes  most  of  the  energy  with  a  very  slight  loss. 
The    track    winding    of  this  relay  requires  very  little  energy. 
Therefore,  the  single-phase  is  better  suited  for  short  blocks  and 
the  two-phase  for  long  ones.     Since  most  of  the  energy  is  fur- 
nished by  the  local  winding,  it  is  possible  to  use  long  track  circuits 
as  compared  with  direct  current.     If  all  the  energy  had  to  be  fur- 
nished through  the  track  winding,  the  block  could  be  practically 
no  longer  than  with  direct  current. 

UNION  SWITCH  AND  SIGNAL  COMPANY  DESIGNS 

155,  Vane  Type.1 — The  two  pole  pieces  in  the  vane  type  of 
alternating-current  relay  are  made  up  of  laminated  iron  cores 

instead  of  solid  iron  cores  as  is  the 
case  with  the  neutral  relay.  Be- 
tween the  two  cores  wound  with 
wires  swings  an  aluminum  vane 
mounted  on  a  horizontal  shaft. 
The  vane  is  constructed  to  swing 
through  an  angle  of  90  degrees. 
The  alternating  current  flowing 
through  the  windings  induces  an 
alternating  flux  in  the  iron  core 
and  in  the  gap  between  the  pole 
~  faces  of  the  core.  A  copper 

Fia.    247.— Operating    element   of    f          -,         -^         «._  .     ,. 

vane  relay.  terrule,    Fig.    247,    encircling    the 

upper  half  of  each  pole  face,  acts 

just  as  a  short-circuited  secondary  on  a  transformer  to  produce 
a  counter  magneto-motive  force  opposing  that  of  the  primary 
1  Proceedings,  Railway  Signal  Association,  1910. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   231 


winding.  This  counter  magneto-motive  force  causes  a  lag  in 
the  passage  of  the  magnetic  flux  through  the  portion  of  the 
pole  face  encircled  by  the  ferrule,  with  the  result  that  the  maxi- 
mum and  zero  values  of  the  magnetic  flux  in  the  part  of  the  pole 
face  encircled  by  the  ferrule  occur  a  short  interval  of  time  after 
the  corresponding  values  are  reached  in  the  other  half.  There  is 
then  a  traveling  of  the  magnetic  field  over  the  pole  face  towards 
the  portion  that  is  enclosed  in  the  ferrule.  These  lines  of  force 
traveling  in  this  direction  carry  the  vane  along  with  them  causing 
it  to  rotate  about  its  axis. 

Model  15  vane  type,  shown  in  Fig.  248  can  be  operated  either 
as  a  two-position  or  a  three-position  relay.     The  two-position 


FIG.  248. — Model  15  vane  type  relay. 

relay  may  have  either  one  or  two  windings.  The  various  arrange- 
ments are  known  as  single-element  two-position,  two-element  two- 
position  and  two-element  three-position.  The  single  element 
is  used  either  on  single-rail  return  or  on  center-fed  double-rail 
return  systems. 

156.  Ironless  Galvanometer  Type. — This  type  can  be  used 
either  in  track  or  line  circuits,  but  it  offers  its  chief  advantage 
when  used  as  a  track  relay.  The  field  or  stationary  winding, 
which  is  the  two  outside  coils,  is  connected  to  the  transmission 
line;  while  the  armature,  which  is  the  movable  element,  is  con- 
nected to  the  track  circuit.  Most  of  the  energy  can  be  supplied 
by  the  transmission  line  leaving  a  very  small  portion  to  be  fur- 
nished by  the  rails.  This  allows  track  circuits  to  be  a  mile  or 
more  in  length  without  excessive  loss  by  leakage.  Current  of 


232 


RAILWAY  SIGNALING 


similar  characteristics  must  flow  through  both  windings  at  the 
same  time  to  make  the  relay  operate.  Direct  current  from  the 
rails  has  no  effect  either  to  operate  or  to  hold  the  armature  since 
it  can  act  only  on  the  one  winding,  which  contains  no  iron. 


FRONT  VIEW 


SECTIONAL   END   VIEW 


GLASS  SECTIONED 

FIG.  249. — Three-position  ironless  galvanometer  relay. 

157.  Iron  Core  Galvanometer  Type. — The  relay  shown  in  Fig. 
250  is  a  two-phase  wire  wound  type  whose  operation  depends 
upon  the  phase  relations  of  the  current  in  the  track  and  trans- 
former windings.  It  is  built  in  the  form  of  a  motor  in  which  the 


SECTIONAL   BACK   VIEW  SECTIONAL  SIDE  VIEW 

FIG.  250. — Iron  core  galvanometer  relay. 

armature  makes  only  a  part  of  a  revolution,  and  the  field  and 
armature  are  connected  in  multiple  or  are  excited  from  separate 
sources.  Its  characteristics  are  very  similar  to  the  Ironless  type, 
and  it  is  generally  interchangeable  with  it  for  steam-road  service. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   233 


It  is  not  recommended  for  electric-road  practice.     It  is  slightly 
more  economical  of  current  than  the  Ironless  type. 

158.  Centrifugal  Frequency  Relay.1 — The  frequency  relay  is 
designed  for  use  in  the  track  circuits  of  a  railroad  having  alter- 
nating current  for  both  propulsion  and  signaling.  The  number 
of  revolutions  per  second,  n,  at  which  an  induction  motor  oper- 

2/ 
ates  is  calculated  from  the  formula,  n  =  ^  where  /  is  the  cycle 

frequency  of  the  stator  winding,  and  P  is  the  number  of  stator 
poles.     If  a  current  should  have  60  cycles  per   second  and  a 


FIG.  251. — Centrifugal  frequency  relay. 

stator  12  poles,  the  motor  would  make  10  revolutions  per  second; 
while  if  the  current  should  have  25  cycles  per  second  and  the 
same  number  of  poles,  the  rotor  would  make  a  little  over  4 
revolutions  per  second. 

The  stator  windings  of  the  Union  frequency  relay  is  made 
up  of  two  elements  so  that  the  instrument  may  operate  either  as 
a  single-element  or  two-element  relay.  The  proper  phase  relation 
of  the  current  flowing  through  the  two  windings  is  adjusted  by 
inserting  suitable  resistances  in  the  circuits.  The  centrifugal 
apparatus  is  constructed  somewhat  after  the  manner  of  the 
governor  on  a  steam  engine.  With  60-cycle  current  the  rotor 
turns  with  sufficient  speed  to  cause  the  balls  to  swing  out  far 

1  Signal  Engineer,  February,  1914. 


234 


RAILWAY  SIGNALING 


enough  to  lift  the  operating  collar  the  proper  amount  for  closing 
the  contacts.  With  25-cycle  current  the  rotor  does  not  acquire 
sufficient  speed  to  lift  the  centrifugal  apparatus  to  make  the 
necessary  contacts  for  operating  the  signals. 

159.  Radial  Contact  Polyphase  Induction  Type. — This  instru- 
ment, shown  in  Fig.  252,  is  built  on  the  induction  motor  plan 
and  can  be  used  either  as  a  track  or  line  relay.  As  the  shaft 
rotates  it  causes  the  fingers  to  engage  with  contacts  located 
around  the  periphery  of  the  case.  The  chief  advantage  of  this 
type  of  relay  is  its  capacity  for  a  large  number  of  contacts. 


FIG.  252. — Radial  polyphase  relay. 
GENERAL  RAILWAY  SIGNAL  COMPANY  DESIGNS 

160.  Universal  Alternating  Current  Relay. — The  universal 
alternating  current  relay  is  an  induction  type,  with  the  stator 
winding  made  up  of  eight  form-wound  coils  and  with  the  rotor 
shaft  mounted  vertically.  The  contact  movement  is  operated 
by  contact  rolls,  as  shown  in  the  illustration,  Fig.  253.  The 
relay  is  made  either  direct  connected  or  pinion  and  sector  con- 
nected. The  direct  connected  is  recommended  for  average  track 
circuit  conditions,  while  the  pinion  and  sector  connected  is 
recommended  for  long  track  circuits  having  unfavorable  ballast 
conditions  and  for  special  work.  The  relay  may  be  fitted  for 
either  single-rail  or  double-rail  track  circuits,  and  may  also  be 
equipped  for  line  circuits.  It  may  be  converted  to  a  three- 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   235 


position  relay  by  adding  counterweights  and  readjusting  the 
contacts. 


FIG.  253. — Universal  A.  C.  relay. 

161.  Models  2  A  and  2B  Two-  and  Three -position  Relays. — 
The  Model  2A  relay  shown  in  Fig.  254  is  designed  primarily  for 
use  as  a  track  relay  on  steam  roads,  or  electric  traction  lines 
employing  direct  current  for  propulsion.  It  may,  however,  be 
used  as  a  line  relay.  The  construction  of  this  relay  is  very  much 
like  the  two-phase  induction  motor  type  except  that  it  has  a  rotor 
made  of  aluminum,  a  non-magnetic  metal,  instead  of  iron.  One 
phase  of  the  winding  is  energized  by  a  transformer  located  near 
the  relay  and  the  other  by  the  track  circuit. 

These  instruments  are  made  to  operate  either  as  two-position 
or  three-position  relays.  The  two-position  may  have  either  the 
direct-connected  arrangement,  as  illustrated  in  C,  or  the  sector 
and  pinion  arrangement,  as  shown  in  D.  As  the  direct-connected 
relay  is  arranged  with  a  crank  and  lever  directly  connected  to  the 
rotor  for  operating  the  contact  fingers,  it  has  a  quicker  pick-up 
and  drop-away,  but  requires  more  energy  for  operation. 
The  three-position  relay  always  has  the  pinion  and  sector 
arrangement. 

The  Model  2B  is  designed  primarily  for  use  as  a  line  relay, 
although  it  is  employed  as  a  track  relay  on  steam  roads  having 
short  track  circuits.  The  two-position  relay  is  used,  also,  as  a 
track  relay  where  there  are  short  track  circuits  on  electric  lines 
employing  direct  current  for  propulsion.  The  sector  operates  a 
lever  that  lifts  the  fingers  to  make  contact. 


236 


RAILWAY  SIGNALING 


The  Model  2B  Time-element  relay,  has  a  gear  train  in  place  of 
the  pinion  and  sector  movement  for  operating  the  contacts. 
Time-element  relays  are  of  two  kinds:  (1)  Time-element  closing, 


VIEW  SHOWING  CRANK  AND  LEVER  ARRANGEMENT 
FOR  TWO  POSITION   DIRECT-CONNECTED    RELAYS 

c 


VIEW  SHOWING  SECTOR  AND  PINION   ARRANGEMENT 
FOR  THREE   POSITION  RELAYS 


Model  2A  relay. 

FOR  WALL  TYPE  RELAYS  ONLY— i 


Model  2B  relay. 
FIG.  254,  part  1.     Models  2 A  and  2B  relays. 

in  which  the  front  contacts  are  not  made  until  a  predetermined 
time  after  the  relay  is  energized  and  are  immediately  broken 
when  the  relay  is  deenergized.  They  operated  as  single-circuit 
relays  only.  (2)  Time-element  opening,  in  which  the  front 
contacts  are  made  immediately  when  the  relay  is  energized  and 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   237 


are  not  broken  until  a  predetermined  time  after  the  relay  is 
deenergized.     They  operate  as  two-circuit  relays  only. 


Model  2B,  time  element  relay. 
FIG.  254,  part  2.     Models  2A  and  2B  relays. 

162.  Model  2A  Two-position  Centrifugal  Frequency  Relay. — 
The  frequency  relay,  illustrated  by  Fig.  255,  is  designed  prin- 
cipally for  service  as  a  track  relay  for  double-rail  return  circuits 
where  alternating  current  is  used  for  propulsion.  It  is  employed 
on  steam  roads  only  at  crossings  with  electric  lines  having  alter- 


FIG.  255.— A.  C.  relay. 


Model  2 A,  two-position  centrifugal  frequency  type. 
Rotor  operated. 


nating  current  for  propulsion.     It  may  be  used,  also,  on  short 
single-rail  return  circuits  or  as  a  line  relay. 

When  the  track  section  is  not  occupied  by  a  train,  the  rotor 
operates  at  a  speed  proportional  to  the  frequency  of  the  signaling 
current,  which  is  usually  60  cycles  a  second.  When  the  rotor 
turns  at  this  speed  it  rotates  the  centrifuge  apparatus  at  such  a 
rate  as  to  cause  it  to  assume  a  position  more  nearly  at  right 
angles  to  the  axis  of  rotation.  This  causes  a  thrust  on  the  lever 
arm,  which  lifts  the  fingers  to  make  the  proper  contacts  for 
closing  the  signal  circuits.  If  a  train  occupies  the  section  and 
short-circuits  the  signaling  current,  and  the  rotor  runs  at  a 


238 


RAILWAY  SIGNALING 


slower  speed  corresponding  to  that  of  the  propulsion  or  stray 
current  frequency,  the  centrifuge  apparatus  will  not  assume 
the  proper  position  to  cause  the  finger  contact.  This  construc- 
tion prevents  the  propulsion  current  from  operating  the  relay. 
As  the  relay  operates  only  in  one  direction,  it  gives  broken  joint 
protection  when  adjacent  track  feeds  have  staggered  polarities. 

ALTERNATING-CURRENT  TRACK  AND  SIGNAL  CIRCUITS 
163.  Two-position  Signals. — Figure  256  represents  the  track 
and  signal  circuits  installed  on  a  portion  of  the  Subway  in  New 
York.  This  is  a  single-rail  return  system  with  direct-current 
propulsion,  as  was  previously  explained.  The  vane  type  of  relay 
was  used  in  this  installation. 


SATTERY 


FIG.  256. — Track  and  signal  circuits  on  a  portion  of  the  New  York  subway. 
(Union  Switch  and  Signal  Co.) 

Figure  257  illustrates  the  track  and  signal  circuits  used  on  a 
portion  of  the  Long  Island  Railroad.1  This  is  a  center-fed  con- 
struction with  the  vane  type  of  relay  used  at  each  end  of  the  block. 

Figure  258  represents  the  signaling  plan  used  on  another 
portion  of  the  Long  Island  Railroad.  The  track  transformer  is 
attached  to  the  rails  near  the  middle  of  the  track  section,  and  a 
galvanometer  type  of  relay  is  used  at  each  end,  the  one  at  the 
exit  end  of  the  track  circuit  being  a  two-position  and  the  one  at 
the  entrance  end  a  three-position  relay.  The  armatures  of  the 
relays  are  energized  directly  from  the  track  circuit.  The  field 
of  the  relay  at  the  exit  end  of  the  track  circuit  is  energized 
directly  from  the  55-volt  transformer;  the  field  of  the  relay  at 

1  Pages  412  and  413,  Proceedings  Railway  Signal  Association,  1910. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   239 


240 


RAILWAY  SIGNALING 


the  entrance  end  of  the  track  circuit  is  energized  over  the  line 
wire  extending  up  to  the  exit  end  of  the  track  circuit  and  over  the 
point  of  the  relay  at  this  end,  thence  through  the  pole-changer  to 
the  55-volt  transformer. 

The  West  Jersey  and  Seashore  Railroad  signal  installation, 
represented  by  Fig.  259,  has  center-fed  track  circuits  with 
blocks  averaging  about  4,000  ft.  in  length. 1  There  is  a  wire  wound 
armature  type  of  relay  at  one  end  of  the  block  and  a  step- 
up  transformer  at  the  other.  The  step-up  transformer  is  con- 
nected to  the  relay  by  line  wire  furnishing  the  current  for  the 
armature  winding.. 

Figure  260  represents  a  signal  installation  on  a  portion  of  the 
N.Y.N.H.  &  H.R.R.1  The  signal  and  lighting  current  is  110 
volts,  60-cycle  frequency,  stepped  down  from  a  2,200-volt  trans- 

,-?200Volt--25~A.C  Mains 


Inductive  b^srrar'6f<yrmer 
not&hown  '•:•• 


FIG.  258. — Semi-wireless  control,  L.  I.  R.  R.     (Union  Switch  and  Signal  Co.) 

mission  line  fed  from  a  11, 000- volt  power  transmission  line. 
The  track  circuit  equipment  was  designed  for  either  550-volt 
direct-current  or  11, 000- volt,  25-cycle,  single-phase  alternating 
current.  As  it  was  necessary  to  cross-bond  the  track  every 
3,000  ft.,  cut  sections  were  employed  in  each  block.  Current  is 
supplied  to  the  track  circuit  by  a  transformer  located  at  the  middle 
of  the  section.  Frequency  relays  designed  to  operate  at  60 
cycles,  installed  at  each  end  of  each  section,  control  the  signal 
circuits.  There  is  also  an  impedance  bond  at  each  end  of  each 
track  section. 

164.  Three -position  Signals. — Figure  261  illustrates  the  Union 
typical  track  and  signal  circuit  plan  for  three-position  signaling 
arranged  for  direct-current  propulsion  with  double-rail  return. 
1  Proceedings,  Railway  Signal  Association,  1910. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   241 


16 


242 


RAILWAY  SIGNALING 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   243 


244 


RAILWAY  SIGNALING 


Figure  262  is  a  diagram  of  track  and  signal  circuits  installed 

by  the  General  Railway 
Signal  Company  on  a  por- 
tion of  the  Cumberland 
Valley  Railroad,  a  double- 
track  steam  line.  The  sig- 
nal transmission  line  carries 
a  current  of  4,400  volts. 
Transformers  step  the  cur- 
rent down  to  110  volts  for 
the  signal  circuits  and  to 
2,  4,  6,  8,  and  10  for  track 
circuits.  This  range  in 
voltage  is  obtained  by  plac- 
ing an  adjustable  resistance 
^  in  series  with  the  trans- 
'"  former  leads.  All  the  auto- 
matic track  circuits  are 
arranged  for  wireless  con- 
trol by  operating  three- 
position  track  relays.  The 
90-degree,  or  distant  indi- 
cation, is  given  by  reversing 
the  polarity  of  the  track 
circuit  by  means  of  the 
pole  changer  on  the  signal 
mechanism. 

The  track  circuits  vary 
in  length  from  2,000  to 
8,000  ft.  4  volts  are  re- 
quired to  operate  the  track 
circuits  up  to  5,000ft.  and 
6  and  8  up  to  8,000  ft. 
The  relay  is  the  polyphase 
three-position  type,  the 
6  local  phase  being  wound 
for  110  volts.  The  relay 
operates  in  one  direction  to 
bring  the  signal  to  the  45- 

degree  position  and  in  the  reverse  direction  to  the  90-degree 
position.     It  stands  in  the  neutral  position  when  shunted. 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   245 

Figure  263  is  a  diagram  of  typical  circuits  used  by  the  same 
company  in  installing  the  signal  system  on  a  portion  of  the  double- 
track  line  of  the  Southern  Railway.  The  current  furnished  by 
the  signal  transmission  line  has  a  potential  of  4,400  volts.  Trans- 
formers step  the  current  down  for  the  110- volt  induction  motors 
used  to  operate  the  signal  mechanisms  and  for  the  110- volt 
primary  winding  of  the  separate  track  transformers.  The 
secondary  taps  of  the  track  transformers,  arranged  to  secure 
any  voltage  from  1  to  10  in  steps  of  1  volt,  furnish  current  to 

55V.-IIOUorl20V.A.C. 
From  Line  Transformer 


Primary 
Local 


To  Opposite 

Signaled 

Double  Location 

r 

i 

1 1 — r 


Track 


FIG.  263. — Typical  circuits  used  on  the  Southern  Railway. 

energize  the  three-position  track  relays.  The  track  circuits  are 
end-fed  and  are  continuous  from  one  signal  to  the  other,  varying 
in  length  from  300  to  14,000  ft.  The  45-  to  90-degree  movement 
of  the  signal  is  secured  by  a  reversal  of  the  track  transformer 
leads.  In  the  figure,  when  a  12-volt  local  is  used,  the  winding 
on  No.  2  track  transformer  is  omitted  and  the  connection  is  made 
as  indicated  by  the  dotted  lines.  P  is  the  pole-changer  on  the 
signal,  Q  is  the  track  transformer,  usually  the  K-l  type,  R  is  a 
choke-coil  air-gap  arrester,  S  is  a  resistor  in  the  ground  lead  for 
circuits,  T  is  an  air-gap  arrester  without  choke-coil,  U  is  a  low- 
voltage  ground  element,  V  is  a  low-tension  ground  wire,  W  is  the 


246 


RAILWAY  SIGNALING 


signal  pole  or  case,  X  is  an  adjust- 
able track  resistor,  and  F  is  a 
three-position  polyphase  track 
relay. 

Figure  264  shows  a  typical  cir- 
cuit plan  for  signals  installed  on 
the  lines  of  the  New  York 
Municipal  Railway  Corporation. 
It  provides  for  one  full  block 
overlap  with  automatic  train 
stops  used  in  connection  with  the 
signals.  (A)  in  Fig.  265,  shows  the 
control  limits  for  the  circuits, 
while  (B)  shows  the  indications 
of  signals  and  the  positions  of 
automatic  stops  with  a  train  in  a 
block.  The  reason  for  retaining 
the  stop  on  the  first  track  section 
in  advance  of  the  signal  is  that 
occasions  frequently  arise  where  it 
becomes  necessary  to  operate 
trains  against  the  normal  direc- 
tion of  traffic,  and  this  scheme 
provides  a  very  sirnp^  means  of 
automatically  clearing  the  stop  for 
such  moves. 

Normal  ^danger  signals  having 
time-element  control  are  used  on 
down  grade  track  or  on  approaches 
to  sharp  curves  where  it  becomes 
necessary  to  limit  the  speed  of 
trains  regardless  of  whether  or 
not  the  track  is  occupied.  The 
control  is  secured  by  the  use  of 
time-element  relays  in  conjunction 
with  approach  sections  that  are 
generally  two  blocks  long.  The 
control  limits  for  this  scheme  are 
the  same  as  in  (A)  with  the  normal 
danger  time-element  feature  added. 

In  (C)  a  train  approaches  sig- 
nal 5  with  the  track  ahead  un- 


AUTOMATIC  BLOCK  SIGNALING  ON  DOUBLE  TRACK   247 

occupied.  If  the  train  occupies  the  track  between  signals  9  and 
7  for  the  required  time,  for  example  14  seconds,  signal  5  will 
display  a  yellow  or  caution  indication  that  will  cause  signal  7  to 
change  from  a  yellow  to  a  green  indication,  as  shown  in  (D). 
As  the  train  proceeds  and  occupies  the  track  between  signals  7 
and  5  for  the  required  length  of  time,  signal  3  changes  from  a  red 
to  a  yellow  indication  and  this,  in  turn,  causes  signal  5  to  change 
from  a  yellow  to  a  green  indication.  If  the  train  should  pass  over 


(A) 


I         ^  • 

^/re/7          7     »//w         5    /fee/ 
(B) 


^ ^ A 


.A          TO S- 


T^/?€ty  lT^?/Pe/7         lT^8'/A?ir 

(0) 


|Q>  |Q |Q>^^ IQ>  IQ 

Yelfow  Red  Red  Yellow  Red 

(F) 

FIG.  265. — Control  limits  and  indications  on  lines  of  the  New  Yo     fl5B 
Municipal  Railway  Corporation. 

the  track  between  signals  9  and  7  in  too  short  a  time  to  pe 
signal  5  to  change  from  red  to  yellow,  signal  7  would  be  pasted 
indicating  yellow  or  caution,  and  the  train  would  be  forced  to 
occupy  the  track  between  7  and  5  just  about  twice  as  long  as 
would  have  been  the  case  if  it  should  have  waited  and  allowed 
signal  7  to  indicate  green  before  passing  it.  If  the  train  should 
continue  at  a  speed  faster  than  should  be  permitted  and  should 
pass  over  the  track  between  7  and  5  before  the  time-element  relay 
should  have  operated,  the  train  would  be  automatically  tripped 
at  signal  5.  The  time-element  control,  as  used  on  the  Manhattan 


248  RAILWAY  SIGNALING 

and  Williamsburg  bridges,  limits  the  train  speed  on  the  down 
grade  portion  to  about  15  miles  an  hour. 

In  approaching  stations  the  time-element  is  involved  with 
extended  length  of  control.  In  this  case  the  blocks  are  short  and 
the  control  is  extended  to  cover  three  or  more  track  circuits, 
depending  upon  conditions.  The  signals  are  normally  clear  and 
operate  as  shown  in  (E)  and  (F) .  The  long-dashed  lines  indicate 
the  regular  two-block  overlap  control  and  the  solid  lines  indicate 
the  extended  control,  which  is  cut  off  by  means  of  the  time- 
element  relays  if  the  speed  of  a  following  train  is  reduced  as 
predetermined  by  the  timing  of  the  time-element  relays.  (E) 
shows  signal  indications  with  a  train  occupying  the  track  at  a 
station,  while  (F)  shows  how  a  train  may  follow  provided  its  speed 
is  reduced. 

With  train  No.  1  at  the  station,  signals  1,  3,  5,  7,  and  9  indicate 
red,  and  signal  11  yellow.  As  train  No.  2  approaches  signal  11 
at  a  predetermined  reduced  speed,  signal  9  changes  from  red  to 
yellow  allowing  signal  11  to  change  from  yellow  to  green.  As 
train  No.  2  occupies  the  track  between  signals  11  and  9,  signal  7 
changes  from  red  to  yellow  and  signal  9  changes  from  yellow  to 
green.  Thus  each  signal,  11,  9,  and  7,  changes  to  display  a  green 
indication  and  signal  5  changes  to  display  a  yellow  indication 
provided  train  No.  2  approaches  each  at  a  predetermined  reduced 
speed.  With  train  No.  1  still  in  the  station,  train  No.  2  has  to 
stop  at  signal  3.  The  time-element  feature  works  in  practically 
the  same  manner  as  in  the  normal  danger  scheme,  except  that  it  is 
used  to  reduce  the  length  of  control.  That  is,  if  train  No.  2 
exceeds  the  predetermined  speed  the  extended  control  is  not  cut 
off,  the  signals  do  not  change  from  the  red  indication  and  the  train 
is  automatically  stopped. 


CHAPTER  XIV 
AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK 

165.  General. — Automatic  block  signals  provide  for  efficiency 
and  safety  in  operation  on  a  single-track  road  as  well  as  on  a 
double-track  line.     When  a  single-track  line  reaches  the  point  of 
congestion,  the  installation  of  automatic  block  signals  will  relieve 
the    congestion    and    prolong    the    day    when    double-tracking 
becomes  necessary.     The  installation  of  the  signals  requires  very 
little  time,  expense  and  labor  in  comparison  with  the  construction 
of  a  double  track.     Some  roads  report  that  the  capacity  of  a 
single  track  has  been  increased  by  20  per  cent,  with  the  installation 
of  automatic  block  signals. 

166.  Union  General  and  Special  Plans — TDB  System. — In 
double-track  block  signaling,   the  signals  must  protect    trains 

?  2349979$ 

1  1  1  1  1  I  1  f 

Station  A  Station  B  Station  C 


FIG.  266. — Union  plan  of  single  track  signaling. 

that  follow  each  other;  whereas  in  single-track  operation  the 
signals  must  protect  not  only  trains  that  run  in  the  same  direc- 
tion, but  also  those  that  run  in  the  opposing  direction.  In 
order  to  do  this  several  plans  have  been  devised,  one  of  which  is 
the  two-position  scheme  by  the  Union  Switch  and  Signal  Com- 
pany. Figure  266,  shows  the  relative  location  of  home  and 
distant  signals  in  the  case  where  the  stations  lie  about  4  miles 
apart.  Should  the  distance  be  greater,  one  or  more  sets  of 
intermediate  home  signals  should  be  added  in  order  that  the 
blocks  should  not  be  so  long  as  to  cause  delay  to  traffic. 

The  lines  above  and  below  the  signals  in  Fig.  266  represent 
the  length  of  track  that  controls  the  signals  and  holds  them  in  the 
stop  position;  for  example,  the  line  from  signal  1  extends  to  the 
right  as  far  as  the  end  of  the  first  track  section  beyond  signal  4, 

249 


250  RAILWAY  SIGNALING 

and  if  a  train  should  occupy  any  portion  of  the  track  between 
these  two  points  signal  1  would  be  in  the  stop  position.  Like- 
wise, the  control  for  signal  4  extends  to  signal  1  so  that  if  a  train 
should  be  at  any  point  between  signals  1  and  4,  signal  4  would  be 
in  the  stop  position.  A  train  leaving  station  A  and  moving  to 
the  right  will  place  4  to  the  stop  position  as  soon  as  it  passes 
signal  1,  and  a  train  moving  to  the  left  will  place  signal  1  in  the 
stop  position  as  soon  as  it  enters  the  section  to  the  right  of 
signal  4.  This  overlap  of  one  track  section  affords  head-on 
protection  and  eliminates  the  possibility  of  trains  passing  signals 
4  and  1  both  in  the  clear  positions  at  the  same  time. 

The  reason  for  placing  signals  3  and  4  one  track  section  apart 
is  for  head-on  protection  also.  Should  opposing  trains  pass 
signals  1  and  6  at  the  same  time,  they  would  stop  at  signals  3 
and  4  with  a  full  track  section  between  them. 

There  is  a  home  signal  at  the  beginning  and  end  of  each  siding. 
The  distant  signals  are  governed  by  the  siding  entrance  signals. 
The  control  for  home  signal  5  extends  to  distant  signal  8  and  the 
control  for  home  signal  8  extends  to  distant  signal  5.  As  soon 
as  a  train  moving  to  the  left  passes  distant  signal  8,  the  home  and 
distant  signals  5  will  go  to  the  stop  and  caution  positions.  As 
soon  as  it  passes  home  signal  8,  signal  10  will  assume  the  proceed 
position.  This  arrangement  allows  a  train  occupying  the  main 
track  within  the  station  limits  to  be  fully  'protected  from  trains 
approaching  on  either  side;  at  the  same  time,  since  signals  3 
and  10  both  give  proceed  indications  under  these  conditions,  a 
train  can  reach  the  siding  without  passing  any  home  signal  set 
at  the  stop  position  except  the  siding  entrance  signal  near  the 
switch. 

Sometimes  where  the  distance  between  stations  is  short,  home 
signals  are  placed  only  at  stations,  as  shown  in  (A),  Fig.  267. 
Sometimes  where  the  distance  is  the  ordinary  length  they  are 
placed  at  the  stations  only  for  protecting  trains  within  station 
limits.  The  control  between  stations 'is  as  shown  in  (A),  Fig.  267, 
and  that  through  stations  as  shown  in  (B).  A  preliminary  over- 
lap section,  as  shown  at  Station  A,  Fig.  267,  is  generally  made  in 
favor  of  superior  trains  so  that  two  trains  will  not  pass  at  the 
same  time  home  signals  set  at  the  proceed  position. 

Figure  268  is  a  wiring  plan  for  the  signals  in  Fig.  266.  Figure 
269  is  a  wiring  plan  where  intermediate  signals  come  opposite 
distant  signals,  which  frequently  occurs  in  continuous  blocking 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    251 


4 


*/, 


CO 


!' 


*% 


l 


IS 


I 


r 


:    .1 


252 


RAILWAY  SIGNALING 


where  stations  are  not  over 
2J£  or  3  miles  apart.  Fig- 
ure 270  shows  the  location 
of  home  signals  at  the  end  of 
the  siding  with  some  details 
of  trunking  arrangements. 

Figure  271  represents  a 
different  Union  plan  of  two- 
position  signaling.  This  sys- 
tem was  installed  on  13.2 
miles  of  single  track  on  the 
Washington,  Baltimore  and 
Annapolis  Electric  R.  R.,  a 
freight  and  passenger  inter- 
urban  line  having  1,200- volt 
direct-current  power  for  pro- 
pulsion purposes.  There  are 
eight  standard  blocks  and 
one  special,  employing  17 
semaphore  signals  and  16 
light  signals.  The  longest 
block  is  11,610  ft.  and  the 
shortest  is  5,430  ft.  with  an 
average  of  8,680  ft.  There 
are  four  signals  for  each 
block,  which  extends  from 
one  siding  to  another.  Two 
of  the  signals  are  the  sema- 
phore type,  located  at  each 
end  of  the  block;  the  other 
two  are  the  color-light  type, 
each  about  1,000  ft.  in  ad- 
vance of  a  semaphore  signal. 

The  double-rail  return  sys- 
tem is  employed  with  track 
sections  extending  the  full 
length  of  the  block.  One 
track  relay  is  located  at 
each  end  of  the  track  cir- 
cuit and  is  energized  by  a 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    253 

transformer  feeding  at  the  middle  of  the  block.  The  relay  at 
the  west  end  of  the  block  is  controlled  by  the  track  to  a  point 
about  1,000  ft.  east  of  the  center  of  the  block,  while  the  relay  at 
the  east  end  is  controlled  by  the  track  to  a  point  the  same  dis- 
tance to  the  west  of  the  center.  Each  semaphore  signal  is 
controlled  by  both  track  relays,  while  each  light  signal  is  con- 


FIG.  269. — Wiring  plan  where  intermediate  signals  come  opposite  distant  signals. 

trolled  by  the  relay  at  the  opposite  end  of  the  block.  An  east- 
bound  car  entering  the  block  with  signal  115  at  clear,  places 
this  signal  as  well  as  102  and  104  in  the  stop  position.  xAs  the 
car  passes  113  at  clear  and  reaches  the  western  control  limit  of 
this  signal,  it  sets  113  in  the  stop  position.  As  soon  as  the  car 
passes  102,  all  signals  in  the  block  assume  the  proceed  position. 


Signal  foundation. 


Siynol  fkuadmtlta 

FIG.  270. — Arrangement  for  the  location  of  a  home  signal  at  the  end  of  a  siding. 

The  light  signals  would  act  as  a  check  should  two  approach- 
ing trains  pass  opposing  semaphores  at  the  same  time ;  for  example, 
if  an  east-bound  car  should  pass  signal  115  at  the  same  time  that  a 
west-bound  car  should  pass  102,  the  east-bound  car  would  be 
stopped  by  signal  104  and  the  west-bound  by  signal  113. 


254 


RAILWAY  SIGNALING 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    255 


From  the  2,200-volt  signal  transmission  line  current  is  stepped 
down  to  110- volt  for  signal  circuits  and  to  10- volt  for  track  cir- 
cuits. Each  light  signal  is  controlled  by  a  110- volt  line  relay, 
which  is  in  turn  controlled  by  the  galvanometer  type  of  track 
relay.  The  lamps  behind  the  green  lens  are  controlled  by  the 
front  contact  of  the  line  relay,  while  those  behind  the  red  lens  are 
controlled  by  the  back  contact  of  the  same  relay.  The  semaphore 
signals  are  controlled  by  contacts  on  the  track  relays  and  also 
by  contacts  on  the  light  signal  line  relay,  without  the  use  of  extra 


FIG.  272. — Upper  left-hand  quadrant  semaphore  signals  on  the  Washington, 
Baltimore  and  Annapolis  Electric  R.  R. 

line  relays.  The  semaphore  arm  operates  in  the  upper  left-hand 
quadrant  as  illustrated  by  Fig.  272. 

The  "T  D  B"  (Traffic  Direction  Block)  system  is  another 
scheme  devised  for  single-track  signaling  used  largely  in  interurban 
service.1  The  length  of  block  for  opposing  movements  is  the 
distance  from  one  siding  to  the  next,  while  the  length  for  follow- 
ing movements  is  just  half  the  distance  between  sidings;  that  is, 
there  are  two  "following"  blocks  in  each  "opposing"  block. 
There  are  four  signals  in  each  "opposing"  block,  two  near  the 
ends  of  the  sidings  and  two  near  the  middle  of  the  block.  The 

1  Pages  351-363,  A.  C.  Signaling,  U.  S.  &  S.  Co, 


256  RAILWAY  SIGNALING 

control  limits  for  the  different  signals  are  shown  by  Fig.  273. 
Each  signal  at  a  siding  governs  both  "opposing"  signals  in  the 
block,  while  the  intermediate  governs  only  the  one.  All  signals 
govern  to  the  first  signal  in  the  rear  for  following  movements. 
The  circuits  of  the  entire  system  are  operated  by  alternat- 
ing current.  The  signal  transmission  line  carries  a  potential  of 
2,200  volts  and  from  this  the  current  is  stepped  down  by  trans- 
formers to  110  volts  for  signal  circuits  and  to  10  volts  for  track 
circuits.  The  double-rail  return  system  is  employed  for  the 
propulsion  current. 


LINES  LEADING  FROM  SIGNALS  INDICATE   SECTIONS  OF  TRACK   GOVERNED  AS  FOLLOWS 

^FOR  EAST  BOUND  CARS  ONLY  -- FOR  WEST  BOUND  MRS  ONLY =  FOR  EAST  4  WtST  BOUND  CARS 

NOTE-  An  east  bound  car  between  sidings  blocks  all  west  bound  cars  from  same  territory,  and  vice  versa 
A  car  on  a  siding  does  not  affect  the  signals 

FIG.  273. — Signal  control  limits. 

Figure  274  shows  the  indications  given  by  each  signal  as  one 
or  more  cars  proceed  through  the  blocks.  In  case  A,  there  is 
a  west-bound  car  approaching  the  siding  x,  and  the  opposing 
signal  2  is  in  the  stop  position.  In  B,  the  car  is  passing  signal  1, 
setting  it  in  the  stop  position,  and  also  setting  signals  4  and  6  in 
the  stop  position.  Signal  2  goes  to  clear  as  soon  as  the  train 
passes  out  of  its  block.  In  D,  the  first  car,  R,  has  proceeded  to 
signal  3,  and  a  following  car  has  approached  signal  1.  Signal  1 
protects  car  R  from  a  following  car,  while  signals  4  and  6  protect 
it  against  an  approaching  car.  As  car  R  has  passed  signal  4 
in  E,  signal  1  has  cleared  for  car  S.  In F,  car  S  has  entered  the  first 
"following"  block,  while  car  R  is  in  the  second  "following" 
block.  Signals  1  and  3  protect  against  following  movements  and 
signals  4  and  6  against  opposing  movements.  In  G,  car  R  has 
entered  the  next  "opposing"  block  while  car  S  is  following  and 
both  are  protected  by  signals  in  the  front  and  rear.  The  operation 
for  east-bound  cars  is  similar. 

H,  I,  J,  K  and  L,  show  the  positions  of  cars  and  the  indica- 
tions of  signals  as  the  cars  meet  at  siding  Y.  Cars  between 
X  and  Y  do  not  in  any  way  affect  the  signals  between  Y  and  Z  as 
M,  N,  0,  P,  and  Q  indicate. 

Each  opposing  block  has  one  track  circuit  with  a  relay  at 
each  end  operated  by  current  from  a  transformer  located  at  the 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    257 

middle  of  the  block.  In  the  block  X-Y,  Fig.  275,  there  wiU  be 
one  track  relay  at  signal  1  and  another  at  signal  6.  Normally, 
signals  1  and  6  are  controlled  by  both  track  relays,  or  the  entire 
section  of  track  between  signals  1  and  6.  Signal  3  is  controlled 
by  the  track  relay  at  signal  6,  and  signal  4  is  controlled  by  the 
track  relay  at  signal  1. 


JU  f *» 


^» 


FIG.  274. — The  TDB  system;  effect  of  train  movements  on  signal  indications. 

A  west-bound  car  entering  the  block  X-Y  at  X,  will  deenergize 
the  track  relay  at  signal  1,  thereby  setting  signals  1,  4  and  6 
to  the  stop  position.  As  signal  3  is  controlled  by  the  track 
relay  at  signal  6,  it  will  not  be  set  at  stop  until  the  car  reaches 
the  point  where  it  affects  this  track  relay. 

The  car  in  deenergizing  relays  Tl  and  4L,  energizes  stick 
relay  3$  which  is  used  to  clear  signal  1  after  a  car  has  passed 
signal  4.  This  stick  relay  cuts  out  the  control  of  signal  1  from 

17 


258 


RAILWAY  SIGNALING 


the  track  relay  T6  and  the  line  relay  3L.  As  the  car  proceeds, 
passing  signal  3,  the  track  relay  TQ  is  deenergized,  setting  signal 
3  at  stop  and  still  holding  the  other  three  signals  at  stop.  When 
the  car  passes  signal  4,  track  relay  Tl  is  again  energized  and 
signal  1  is  cleared.  Incidentally,  signal  4  is  cleared  because  the 
track  relay  at  signal  1  is  energized,  but  this  has  no  effect  on  west- 
bound movements.  When  the  car  has  passed  signal  6  all  signals 
and  relays  again  assume  their  normal  positions  unless  a  second 
car  has  entered  the  block  at  signal  1  before  the  first  car  passed 
signal  6.  The  operation  for  east-bound  cars  is  similar. 


FIG.  275. — Circuit  scheme  for  TDB  system. 

The  stick  relay  3$  is  active  only  in  connection  with  west- 
bound movements;  east-bound  movements  have  no  effect  upon 
it.  Therefore,  an  east-bound  car  will  set  signal  1  at  stop  when 
signal  6  is  passed.  Another  stick  relay  4S,  is  used  to  limit  the 
control  of  signal  6  in  a  similar  manner  for  east-bound  movements. 

The  circuits  are  so  arranged  that  but  one  of  the  two  line 
relays  can  be  energized  at  any  one  time.  It  will  be  evident  that 
if  west-bound  car  should  pass  signal  1  at  the  same  time  that  an 
east-bound  car  should  pass  signal  6,  signals  3  and  4  being  directly 
controlled  by  the  track  relays,  would  afford  positive  protection. 

Figure  276  represents  a  single-block  "T  B  D"  installation  with 
four  color-light  signals  on  the  Cleveland,  Southwestern  and 
Columbus  Railway  at  Puritas  Junction,  Ohio.1  This  line  is 
electrically  operated,  handling  both  interurban  passenger  and 

1  Volume  XIV,  1917,  Proceedings,  Railway  Signal  Association. 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    259 

freight  service.  It  is  a  double-rail  return  system  having  600- 
volt  direct  current  to  supply  the  trolley  for  propulsion,  and 
2,200- volt,  25-cycle,  single-phase  alternating  current  to  operate 
the  signal  system.  There  are  two  types  of  transformers;  one,  an 
adjustable  filler  type,  T3,  that  steps  the  current  from  2,200  to 
110  volts  for  the  line  circuit  and  from  2,200  to  10  for  the  center-fed 
track  circuit;  the  other,  a  constant-potential  type,  T2,  that  steps 
the  primary  voltage  from  2,200  to  110  for  the  line  circuit  at  each 
end  of  the  track.  The  track  relays  are  the  two-position  galva- 
nometer type  with  110- volt  local  coils,  while  the  line  relays  are 
110-volt,  two-position  vane  type.  The  signals  are  the  Union 


AC.  Lines?;. 


Seciiov.2G~ 

FillerTram.MOOV 
tOlOA/K>VZ5~ 


FIG.  276. — Wiring  plan  for  light  signals  on  the  C.  S.  &  C.  Ry.  at  Puritas  Jet.,  O. 
(Proceedings,  R.  S.  A.,  1917.) 

Model  13,  light  type,  designed  to  give  both  day  and  night  indi- 
cations by  lights  only. 

167.  General  Railway  Signal,  General  and  Special  Plans,  A. 
P.  Block  System. — (A),  Fig.  277,  represents  a  general  arrangement 
of  three-position  signals  for  single  track.  The  full  lines  above 
and  below  the  signals  mark  the  length  of  control  for  the  stop 
position  as  before,  but  the  dotted  lines  shown  in  addition  indi- 
cate the  control  for  the  caution  position.  If  a  train  should  be  at 
any  point  between  signals  1  and  5, 1  would  be  in  the  stop  position. 
If  it  should  be  at  any  point  between  signals  3  and  7,  3  would  be  in 
the  stop  position  and  1  in  the  45-degree  or  caution  position.  In 


260  RAILWAY  SIGNALING 

(B)  a  train  at  any  point  between  signals  3  and  7  would  place  3 
in  the  stop  position  and  1  in  the  caution  position.  In  (A)  signals 
3  and  4  indicate  in  only  two  positions,  stop  and  proceed.  If 
a  train  should  occupy  the  track  between  signals  3  and  7,  signal  3 
should  show  a  stop  position;  but  if  not,  signal  3  should  give  a 
proceed  indication.  Signal  5  should  show  caution  if  there  is  a 
train  between  signals  7  and  10. 

Another  plan  for  three-position  signaling  on  single  track 
has  been  devised,  known  as  the  Absolute  Permissive  System — 
absolute  for  opposing  trains  and  permissive  for  following  trains. 
When  a  train  enters  a  block,  it  sets  all  the  opposing  signals  in 


-----  -,s 


A  "w'^l^""  B 

DIAGRAM  NS  I        ONE  PAIR  or  SIGNALS  BETWEEN  SIDINGS 

w 


DIAGRAM  N9  2        TWO  PAIRS  OF  SIGNALS  BETWEEN  SIDINGS 

FIG.  277. — Three-position  signals  for  single-track. 

that  block  to  stop,  but  controls  only  two  signals  in  the  rear 
just  as  in  double-track  operation.  Figure  279  shows  the  spacing 
of  the  signals  and  the  lengths  of  their  controls.  There  is  one 
permissive  and  one  absolute  signal  at  each  end  of  each  siding  and 
there  are  four  intermediate  permissive  signals  between  sidings. 
An  east-bound  train  leaving  siding  A,  Fig.  279,  sets  2,  4, 
and  6  all  to  stop  and  8  and  10  to  caution;  likewise  a  west- 
bound train  leaving  siding  C  sets  9,  11,  and  13  to  stop  and  5 
and  7  to  caution.  After  the  east-bound  train  passes  2,  2  will 
go  to  clear;  after  it  passes  3,  1  will  go  to  caution;  and  after  it 
passes  5,  1  will  go  to  clear  and  3  to  caution.  Diagrams  Nos.  4, 
5,  6,  7,  Fig.  280,  show  the  positions  the  signals  take  as  a  west- 
bound train  moves  from  B  to  A.  Diagrams  8,  9  and  10  show  the 
positions  that  signals  take  governed  by  two  trains  moving  with 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    261 


equal  speed  in  opposite  directions  from  A  and  C.     Diagram  11 
shows  the  positions  of  signals  when 
one  train  has  reached  the  siding  B 
in  advance  of  the  other  train. 

In  order  that  a  train  may  con- 
trol all  the  signals  ahead  of  it 
between  sidings  for  opposing  move- 
ments, but  only  the  first  two  signals  in 
the  rear  of  it  for  following  move- 
ments, a  stick  relay  is  used  with 
wiring  as  shown  in  (A),  Fig.  281.  In 
this  figure,  H  is  the  control  relay  for 
the  signal  in  block  A,  T  is  the  track 
relay,  and  S  is  the  stick  relay.  The 
circuit  breaker  operated  by  the  signal 
is  closed  when  the  arms  stand  any- 
where between  45  and  90  degrees. 
The  current  that  energizes  relay  S 
flows  through  the  signal  circuit 
breaker  and  the  back  contact  of  track 
relay  in  block  A.  The  holding  cir- 
cuit of  S  is  through  the  back  con- 
tact of  H  and  the  front  contact  of  S 
itself. 

A  train  entering  A  from  left  to 
right  will  deenergize  relay  T  of  that 
block  causing  its  armature  to  drop 
and  to  deenergize  H  until  the  signal 
blade  has  dropped  below  the  45- 
degree  position.  This  is  sufficient 
time  to  energize  S  and  cause  its 
armature  to  make  front  contact,  com- 
pleting a  circuit  through  S  and  its' 
armature  as  long  as  H  is  deenergized. 
This  circuit  now  through  S  is  inde- 
pendent of  the  signal  and  will  con- 
tinue even  though  the  signal  goes  to 
the  stop  position. 

A  train  moving  from  right  to  left 
will  deenergize  relay  T  in  section  B,  breaking  the  circuit  through 
H  and  allowing  the   signal  to  go  to  stop.     As  the  signal  will 


262  RAILWAY  SIGNALING 

be  in  the  stop  position  before  the  train  enters  section  A,  the 
stick  relay  S  will  not  be  energized.  In  (B),  when  a  train  moves 
from  left  to  right,  the  control  relay  H  for  signal  2  becomes 
energized  by  means  of  wire  X  as  soon  as  the  train  passes  signal 
4.  The  wiring  is  so  arranged  through  a  polarized  relay  that 
signal  2  then  goes  to  the  45-degree  position.  When  the  train 
reaches  M,  4  will  go  to  the  45-degree  position  and  2  to  the 
90-degree  position. 

Figure  282  shows  the  wiring  for  two  sidings  with  an  absolute 
and  a  permissive  signal  at  each  end  and  two  pairs  of  intermediate 
signals  opposite  each  other. 


DIAGRAM  SHOWING  'HEAD  ON*  CONTROLS   ONLY 


DIAGRAM  SHOWING    'FOLLOWING'   CONTROLS  ONLY 

A  B  C 

Diagrams  3  and  3a. 
FIG.  279. — Signal  control  and  location  diagram  for  the  A.  P.  block  system. 

Figure  283  is  a  typical  plan  of  the  A.  P.  Block  System  installed 
on  20  miles  of  single  track  on  the  Puget  Sound  Electric  Railway 
operating  between  Seattle  and  Tacoma,  Wash.1  It  is  a  double- 
rail  return  system  with  600- volt  direct-current  power  for  pro- 
pulsion. The  passing  sidings  average  a.bout  2J£  miles  apart. 
There  is  a  starting  signal  for  traffic  in  each  direction  located  at  the 
passing  track,  and  there  are  two  intermediate  signals  between 
sidings.  From  the  60-cycle,  2,200-volt,  transmission  line,  the 
current  is  stepped  down  to  110  volts  for  signal  circuits.  The 
signals  operate  in  three  positions  in  the  upper  left-hand  quadrant. 

168.  Other  Installations. — Figure  284  represents  a  typical 
wiring  diagram  of  a  37-mile  installation  of  alternating-current 

1  Proceedings,  Railway  Signal  Association,  1915. 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    263 


2 


DIAGRAM  N9  4 


2 


12  14 


-5          V        -V 


U  13 


DIAGRAM  N°  5 


, 7  , 9 

DIAGRAM  N9  6 


K) — •"  12 


7  9  II 


B 
DIAGRAM  Nfi  7 


10 


5  | 7  t 9 

DIAGRAM  N5  8 


JL, 


DIAGRAM  N°  9 


,1-       , 


II  13 


DIAGRAM  N2  10 


_  2 


-i7     ^     -V 

DIAGRAM  N9  II 
FIG.  280. — A.  P.  block  system  diagrams. 


264 


RAILWAY  SIGNALING 


signaling  on  the  N.  &  W.  Ry.1  The  circuits  are  the  "T.  D.  B." 
type  with  such  modifications  as  are  required  for  local  conditions. 
The  bracket  signals  at  the  ends  of  passing  tracks  are  absolute 
signals;  all  others  are  permissive.  The  signals  operate  with  a 
25-cycle  single-phase  current  fed  by  a  4,400-volt  separate  trans- 
mission line  from  the  power  house.  They  are  lighted  by  1 10- volt, 
10-watt  carbon  filament  lamps.  There  are  two  bulbs  in  each 
lamp,  one  burning  continuously,  with  a  relay  to  cut  in  the  second 


TST 


(A) 


FIG.  281. — A.  P.  block  system  circuits. 

in  case  of  failure  of  the  first.  The  blocks  between  passing  sidings 
are  approximately  4,500  ft.  long.  Model  15  polyphase  vane  two- 
position  relays  with  110-volt  local  current  and  4- volt  track 
current  are  used  on  all  track  circuits.  Polarized  line  circuits 
operate  with  Model  15  polyphase  vane  type  of  relays  having 
110-volt  line  and  110-volt  local  current.  All  other  line  circuits 
operate  with  vane  type  of  relay. 

1  Proceedings,  Railway  Signal  Association,  1917,  page  448. 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    265 


266 


RAILWAY  SIGNALING 


Figure  286  is  typical  of  the  automatic  signal  installation 
on  the  electrified  portion  of  the  C.  M.  &  St.  P.  R.  R.  in  Montana. 
The  signal  system  is  fed  by  a  4,400-volt  single-phase  line  carried  on 
the  trolley  poles.  This  current  is  obtained  from  the  2,300/4,400- 
volt  step-up  transformer  on  the  secondary  side  of  the  power 
transformers  that  feed  the  motor-generator  sets  at  the  substations, 
which  are  located  about  35  miles  apart.  The  2,300-volt  current 


FIG.  283. — A.  P.  block  system  on  the  Puget  Sound  Electric  Railway. 

for  these  sets  is  stepped  down  by  transformers  from  the  100,000- 
volt  power  transmission  line.  The  2,300/4,400-volt  step-up 
transformer  is  a  25  k.v.a.,  single-phase,  60-cycle  transformer. 
The  4,400-volt  winding  feeds  the  signal  circuits  on  each  side  of  the 
sub-station.  Each  signal,  circuit  is  controlled  by  a  200-amp., 
4,500-volt  oil  switch  so  that  failure  or  other  troubles  will  be 
limited  to  comparatively  short  sections.  Each  sub-station  in 
the  automatic  signal  territory  is  equipped  with  transformers, 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  TRACK    267 


268 


RAILWAY  SIGNALING 


AUTOMATIC  BLOCK  SIGNALING  ON  SINGLE  BLOCK     269 

switches,  relays,  recording  and  other  apparatus  shown  in  Fig. 
287  for  controlling  the  4,400-volt  signal  line. 

The  transformers  step  the  current  down  from  4,400  volts  to 
110  volts,  60-cycle,  single-phase  current  for  signal  and  other  pur- 
poses; while  track  transformers  step  the  current  from  110  volts  to 
1-18  volts.  The  track  circuits  are  the  double-rail  return  system 
with  end  feed  when  the  length  does  not  exceed  7,500  ft.,  and  with 
center  feed  when  they  do  exceed  this  distance.  The  relays  are : 


FIG.  286. — Arrangement  of  apparatus  at  double  signal  location,  C.  M.  &  St.  P. 
Ry.     (Proceedings,  R.  S.  A.,  1917.) 


Model  15  vane  type,  60-cycle,  single-phase,  two-element,  two- 
position,  for  track  circuits ;  and  Model  15,  two-element  three-posi- 
tion, vane  type,  both  simple  and  slow-releasing,  and  Model  15, 
single-element,  two-position  vane  type,  operating  as  a  stick  relay 
for  line  circuits.  The  normal  voltage  for  the  rail  element  of  the 
track  relay  is  about  1  volt,  while  that  for  the  local  element  is 
110  volts.  Where  the  maximum  grade  does  not  "exceed  1.6 
per  cent.,  impedance  bonds  of  500  amp.  capacity  with  direct- 
current  resistance  of  0.0014  ohm  are  used;  and  where  the  grades 


270 


RAILWAY  SIGNALING 


.exceed  this  value,  bonds  of  1,500  amp.  capacity  with  direct- 
current  resistance  of  0.0003  ohm  are   used.     The  signals  are 

To  Trans  former 

Se/ecfor  5u//fcrffj 
/l/x-tf  #uto  zoo  srsDw/saoff/' 


FIG.  287.— Typical  substation  wiring  for  feeding  signal  circuit  on  C.  M.  &  St.  P. 
Ry.    (Proceedings,    R.  S.  A.,  1917.) 

three-position  color-light  type  for  giving  both  day  and  night 
indications.1 

1  Proceedings,  Railway  Signal  Association,   1917,  and  Signal  Engineer. 
September,  1917. 


CHAPTER  XV 
SIGNAL  MECHANISMS 
TWO-POSITION  SIGNALS 

169.  Hall  Disc  Signal. — The  Hall  disc  signal  consists  of  a 
cloth  disc  17  in.  in  diameter  for  giving  day  indications  and  a  lamp 
with  a  glass  or  roundel  6J^  in.  in  diameter  for  giving  night 
indications.  The  disc  and  roundel  are  mounted  on  aluminum 
arms  that  are  fastened  to  the  Z-shaped  armature  of  an  electro- 
magnet as  shown  in  Fig.  288.  The 
larger  disc  is  made  by  fastening  a 
piece  of  cloth  over  a  wire  hoop,  a 
red  cloth  being  used  for  home 
signals  and  a  yellow  or  green  cloth 
for  distant  signals.  The  day  stop 
or  caution  indication  is  given  by 
exposing  the  full  disc  to  the  view  of 
the  engineman;  the  proceed  indica- 
tion is  given  by  withdrawing  the  disc 
from  view,  showing  in  its  stead  the 
white  background  on  the  inside^  of 
the  signal  case.  The  night  stop  or 
caution  indication  is  given  by  hav- 
ing the  red  or  green  roundel  stand 
in  front  of  the  signal  lamp;  the  pro- 
ceed indication  is  given  by  having 
the  roundel  swing  aside  exposing  the 
lamp  and  giving  a  white  light. 

The  signal  is  moved  to  the  clear 
indication  when  the  Z-shaped  arma- 
ture that  supports  the  colored  discs  is  rotated  between  the  poles 
of  an  electro-magnet  as  shown  in  Fig.  289.  The  "hold  clear" 
mechanism  is  made  up  of  a  set  of  high  resistance  coils  whose  arma- 
ture is  a  flat  bar  fastened  to  the  Z  armature  of  the  clearing  coils. 
Just  as  the  clearing  coils  pull  the  disc  to  the  complete  clear 
position  they  operate  the  circuit  breaker  to  place  the  clearing 
and  the  holding  coils  in  series.  The  total  resistance  diminishes 

271 


FIG.    288.  —  Hall    disc   signal 
mechanism. 


272 


RAILWAY  SIGNALING 


the  flow  of  the  current  to  the  minimum  necessary  to  hold  the 
signal  clear,  for  it  requires  much  less  current  to  hold  the  signal 
clear  than  it  does  to  operate  it.  In  the  normal  clear  system  the 
signals  stand  cleared  except  when  the  block  is  occupied  by  a  train. 
The  operating  mechanism  is  all  enclosed  in  a  combination  metal 
and  wooden  case  mounted  on  top  of  a  pole  of  suitable  height. 


Glass  Disc 


Pole  Pieces 
"Cloth  Di&c^^ 

FIG.  289. — Electro-magnets  and  Z-armature. 

170.  Union  Style  "B"  Signal.— Figure  290  shows  the  operating 
mechanism  for  a  Union  Style  "B"  two-position  signal  where  the 
home  and  distant  signals  are  on  the  same  mast.  The  motor,  M, 
connected  in  the  signal  circuit  has  on  the  end  of  its  armature 
shaft  a  small  pinion,  which  by  means  of  a  train  of  intermediate 
gears,  drives  an  endless  chain,  10.  This  has  in  one  of  its  links 
a  trunnion,  12,  that  under  certain  conditions  lifts  a  slot  arm,  A, 
to  which  is  fastened  the  up-and-down  rod,  6,  that  operates 
the  signal  blade.  The  slot  arm  is  pivoted  near  the  right-hand 
end.  When  the  electro-magnet,  7,  on  the  slot  arm  is  energized, 
the  arm  becomes  rigid,  and  as  the  motor  armature  rotates,  the 
trunnion  lifts  the  fork-head,  5,  of  the  slot  arm  and  clears  the 
signal.  When  the  arm  reaches  the  height  where  the  signal  is 
fully  cleared,  the  lugs  on  the  sides  of  the  fork-head,  5,  are  caught 
by  the  hooks  on  pawl  24  and  the  signal  is  held  in  the  clear  posi- 
tion. The  top  of  the  slot  arm  makes  contact  with  30,  breaking 
the  circuit  to  the  motor  and  making  contact  for  closing  the  circuit 
to  the  distant  signal. 

The  distant  slot  magnet  is  made  with  two  windings  about  the 
same  core,  one  a  low-resistance  winding  in  series  with  the  motor 
to  energize  the  magnet  and  yet  allow  a  sufficient  amount  of 
current  to  flow  to  the  motor,  the  other  a  high-resistance  winding 
in  multiple  with-  the  motor  to  keep  the  magnet  energized  when 


SIGNAL  MECHANISM 


273 


the  motor  is  cut  out  and  yet  reduce  the  amount  of  current,  for 
less  is  required  when  used  only  for  holding  purposes.     A  wiring 


FIG.  290. — Style  "B"  two-position  signal  mechanism. 

diagram  for  direct-current  control  is  shown  in  Fig.  291.     The 
signals  stand  at  the  proceed  position  except  when  the  block  is 


NOTE:  Contact  /opens  and 2 and 3  cloze 
ju&fas  fhehomesignalreache? 
&>e  full  clear  position 

FIG.  291. — Wiring   diagram    for   style   "B"   signal   when  operated   by  direct 
current  and  controlled  by  polarized  relay. 

occupied  by  a  train.     When  the  slot  magnets  become  deenergized, 
the  armature,  T,  falls  away  by  gravity  releasing  H,  TFand  L,  Fig. 
is 


274 


RAILWAY  SIGNALING 


FIG.  292.— Style  "B"  slot  arm. 


Distant  Contrv  I 


Home  Control 

^NOTE:  Contact  / opens  and  2 and 3 dose 
just  as  the  home  signal  reaches 
the  full  clear  position 

FIG.  293.— Wiring  diagram  for  style  "  B"  signal  when  operated  by  alternating 

current. 


SIGNAL  MECHANISM 


275 


292,  thereby  destroying  the  rigidity  of  the  arm  and  allowing  the 
signal  to  go  to  the  normal  position  by  gravity.  The  dashpot 
on  the  rear  of  the  machine  serves  to  diminish  the  shock  of  the  fall. 
There  are  two  sets  of  chains  operated  by  the  same  motor,  one  to 
clear  each  signal  arm.  Figure  293  is  a  wiring  arrangement  when 
the  signal  is  operated  by  alternating  current  instead  of  direct 
current. 

THREE-POSITION  SIGNALS 

171.  Union  Electro -pneumatic  Signal. — Figure  294  illustrates 
the  principle  of  three-position  semi-automatic  signal  movement 


FIG.  294. — Diagram  showing  the  operation  of  three-position    semi-automatic 

signals. 

controlled  by  both  electro-pneumatic  interlocking  and  polarized 
track  circuits.  While  there  is  a  valve  and  magnet  for  both 
45-  and  90-degree  positions,  the  air  supply  from  the  main  comes 
only  to  the  45-degree  valve.  The  supply  for  the  90-degree 
position  comes  from  the  45-degree  cylinder,  an  arrangement 
which  insures  that  if  the  air  or  current  to  either  the  45-  or  90- 
degree  positions  should  be  cut  off,  the  signal  would  recede  from 
the  vertical  to  the  caution  or  stop  position  respectively. 

172.  Union  Style  "S"  Signal.— The  Style  "S"  mechanism 
shown  in  Fig.  295  is  an  outgrowth  of  Style  "B"  to  meet  the 
requirements  of  three-position  signaling.  The  equipment  may 


276 


RAILWAY  SIGNALING 


be  designed  to  operate  with  either  direct  or  alternating  current. 
It  has  only  one  slot  arm,  but  it  has  two  fork-heads  and  operates 
with  two  chains.  The  lower  chain  raises  the  arm  from  the  stop 
to  the  caution  position,  and  the  upper  one  from  the  caution  to 
the  proceed  position. 


FIG.  295. — Style  "S"  D.C.  motor  mechanism. 

173.  Union  Style  uT-2"  Signal.— The  Union  "T-2"  top-post 
three-position  upper  quadrant  signal  is  made  to  operate  with 
either  a  direct-current  or  an  alternating-current  mechanism. 
The  direct-current  equipment,  shown  in  Fig.  296,  consists  of  an 
electric  motor  that  drives  a  train  of  gears  to  operate  the  sema- 
phore shaft,  a  direct-current  controller,  and  an  appliance  for 
holding  the  signal  in  the  proceed  or  caution  position.  The 
holding  mechanism  is  placed  at  the  outer  end  of  the  armature 


SIGNAL  MECHANISM 


211 


shaft.     It  consists  of  a  ratchet  connection,  shown  in  Fig.  297, 
that  engages   the   shaft  only  when   the   motor  is   moving  the 


FIG.  296.— Style    "T-2"    D.C.   signal   mechanism.     Parts   cut   away   to  show 

construction. 

semaphore  to  the  caution  or  the  clear  position.     Connected  to  the 
ratchet  are  three  stop  blades  held  by  the  drum  5.     Directly  below 


E  F 

FIG.  297. — Diagram  of  style  "T-2"  D.C.  signal  mechanism  and  parts. 

the  stop  drum  is  the  slot  magnet  constructed  very  much  like  the 
pin  valve  used  in  electro-pneumatic  mechanisms.  When  the 
magnet  is  energized,  arm  42  is  raised  carrying  with  it  the  steel 


278 


RAILWAY  SIGNALING 


roller,  15,  and  the  contact  finger  41,  closing  the  motor  circuit  at 
20.  As  the  stop  drum  rotates,  the  blades  come  in  contact  with 
the  roller  stopping  the  drum,  but  allowing  the  armature  to  turn 
on  account  of  the  ratchet.  When  the  motor  is  clearing  the 
semaphore,  the  ratchet  does  not  engage  with  the  pawls  in  the 
stop-drum  and  consequently  it  does  not  revolve,  being  prevented 
from  doing  so  by  one  of  the  stop  blades  coming  in  contact  with 
roller  15.  When  the  slot  magnet  is  deenergized  the  arm  42  drops 
by  gravity.  When  the  signal  blade  drops  to  the  caution  or 


FIG.  298. — Mechanism  wiring  for  low  voltage  style  "T-2"  signal. 

stop  position,  it  runs  the  motor  backwards  generating  a  current 
tha*t  it  drives  through  a  resistance  coil,  thus  retarding  the  motor 
ant  "ieving  the  shock  as  the  blade  comes  to  rest. 

Fit  —e  298  represents  the  mechanism  wiring  for  a  direct- 
current  Signal  to  be  operated  by  a  current  with  less  than  30 
volts.  Ifae  circles,  numbered  from  1  to  8,  represent  the  contact 
segments  of  the  circuit  controller.  8  controls  the  motor  circuit, 
7  brings  the  slot  under  the  control  of  the  90-degree  control  relay 
when  the  semaphore  arm  is  at  the  caution  position,  and  1  prevents 


SIGNAL  MECHANISM  279 

this  relay  from  energizing  until  the  signal  reaches  the  caution 
position. 

The  signal  arm  is  moved  from  the  stop  to  the  caution  posi- 
tion by  first  energizing  the  slot  magnet  19  through  the  45-degree 
control  wire  A,  segment  7,  wire  B,  low-resistance  winding  of  the 
slot  coil,  wire  C,  contact  22,  wire  D,  motor,  and  common  wire. 
The  slot  thus  energized  raises  finger  41,  which  opens  contact  22 
and  places  the  high-  and  low-resistance  coils  in  series  with  wire 
E.  This  circuit  complete  to  the  common  wire  holds  the  slot 
energized,  closing  contact  20  and  thereby  completing  the  motor 
circuit  through  wire  Z),  wire  G,  and  segment  8,  to  wire  F.  When 
the  semaphore  arm  reaches  the  caution  position,  segment  8 
opens  the  circuit  to  the  motor,  but  the  slot  remaining  energized 
by  another  route  will  retain  the  signal  in  this  position. 

The  semaphore  arm  is  moved  from  the  caution  to  the  proceed 
position  by  energizing  the  90-degree  control  relay  through  segment 
1 .  The  current  then  flows  through  wire  H  instead  of  through  wire 
A  and  segment  7,  for  7  opens  in  the  first  movement  of  the  sema- 
phore arm  towards  clearing.  Another  contact  on  the  relay 
closes  the  motor  circuit  through  wire  /  and  the  lower  contact  on 
segment  8.  This  segment  opens  when  the  semaphore  arm  reaches 
the  proceed  position,  but  the  coil  serves  to  hold  the  arm  in  this 
position  the  same  as  it  did  in  the  45-degree  position.  The 
jumpers  P  and  Q,  are  added  only  for  two-position  signaling, 
0  to  90  degrees. 

When  the  control  circuits  are  broken  the  slot  magnet  becomes 
deenergized.  The  blade  falls  and  the  motor  becomes  a  generator. 
The  back  point  of  finger  41  makes  contact  at  21  closing  the  local 
"  buffing  circuit"  to  the  motor  through  wire  D,  finger  41,  resis- 
tance 38,  and  wire  E.  The  generator  driving  its  current  through 
the  resistance  38  thus  acts  as  a  brake  at  both  the  45-  and  90- 
degree  positions  of  the  semaphore  arm.  If  only  the  90-degree 
control  relay  is  deenergized,  the  slot  will  be  released  until  contact 
7  is  closed.  The  45-degree  control  circuit  will  then  retain  the 
signal  in  the  caution  position. 

174.  General  Railway  Signal  Model  "2A"  Signal.-  ^ure 
299  shows  the  General  Railway  Signal  Model  "2A,"  ^p-post 
mechanism  for  a  three-position  upper  quadrant  signal.  The 
signal  is  made  with  either  a  direct-  or  an  alternating-current 
mechanism.  The  direct-current  motors  are  made  to  operate 
on  either  a  low  voltage,  8,  10,  and  20  volts,  or  a  high  voltage, 


280 


RAILWAY  SIGNALING 


110  volts.  Formerly,  the  alternating-current  mechanism  voltage 
varied  from  55  to  220,  but  more  recent  practice  employs  induc- 
tion motors  with  a  voltage  of  110. 


FIG.  299. — Model  2A,  top-of-mast  mechanism. 

The  most  common  low-voltage  direct-current  type  of  equip- 
ment is  made  to  operate  at  10  volts  with  a  current  of  2  amp. 
It  is  equipped  with  a  four-pole  series-wound  motor.  The  hold- 
clear  mechanism  is  shown  in  Fig.  300. 
This  retaining  mechanism  is  actuated 
by  a  compound-wound  electro-magnet 
whose  armature  operates  a  pawl  that 
meshes  with  a  toothed  disc  on  the 
motor  shaft.  One  set  of  the  windings, 
having  a  resistance  of  26  ohms,  is  the 
pick-up  coil;  while  the  other  set,  hav- 
ing a  resistance  of  630  ohms,  is  the 
retaining  coil.  In  the  case  of  the 
10-volt  machine,  0.25  amp.  is  required 
to  pick  up  the  armature,  but  only 
0.016  amp.  is  necessary  to  hold  it  and 
hence  retain  the  motor  in  the  caution  or 
clear  position.  The  circuit  controller 
makes  a  contact  just  before  the  signal  blade  reaches  the  45-degree 
and  90-degree  positions  energizing  the  pick-up  coil  and  picking 


FIG. 


300.  —  Retaining   mech- 
anism. 


SIGNAL  MECHANISM 


281 


up  the  hold-clear  armature.  A  second  contact  throws  the  pick- 
up and  holding  coils  in  series  making  a  total  resistance  of  656 
ohms.  As  the  signal  stands  at  the  proceed  position  in  the  normal 
clear  circuit  except  when  a  train  is  in  the  block,  the  current  is 
flowing  through  the  coils  a  very  large  portion  of  the  time,  and 


the  high-resistance  winding  is  used  to  reduce  the  amount  of 
current  to  a  minimum. 

As  soon  as  the  track  relay  becomes  deenergized  by  a  train, 
the  holding  coils  become  deenergized  also,  and  their  armature 
falls  away  by  gravity  allowing  the  signal  to  drop  to  the  caution  or 


282 


RAILWAY  SIGNALING 


stop  position.  The  force  of  the  falling  signal  arm  is  checked  by 
driving  a  current  through  a  resistance  coil.  As  the  blade  drops 
it  operates  the  gears  and  the  motor  in  a  reverse  direction  from 


that  used  to  place  the  signal  at  caution  or  clear.  This  backward 
movement  of  the  motor  makes  it  a  generator;  and  just  before 
the  blade  reaches  its  caution  or  horizontal  position,  this  generator 


SIGNAL  MECHANISM 


283 


drives  its  current  through  the  resistance  coil,  checking  the  fall  of 
the  blade,  thereby  preventing  damage  to  the  equipment. 
Figure  301  shows  the  wiring  diagram  for  low-voltage  direct- 
current  control  of  an  automatic  signal  while  Fig.  302  shows  it 
for  alternating-current  control. 


FIG.  303.— Style  "K"  signal. 


175.  Hall  Three-position  Style  "K"  Signal.— The  Hall  Style 
"K"  three-position  signal  is  made  with  either  a  direct-  or  an 
alternating-current  mechanism.  Figure  303  represents  the  top- 
post  type  built  with  direct-current  equipment.  The  motor 
operates  on  a  vertical  axis  and  drives  the  signal  arm  by  means  of 
a  series  of  gears.  Gear  B,  Fig.  304,  is  attached  rigidly  by  screws 
to  the  hold-clear  clutch  magnet  G.  The  armature  M,  of  this 
magnet  is  supported  on  a  separate  shaft  from  the  gear  B  and 
magnet  G  and  rotates  independently  of  them.  The  blade  is 
held  in  the  caution  or  clear  position  by  energizing  the  magnet  G 
causing  a  friction  contact  between  the  magnet  surface  and  the 
outside  bronze  rim  on  the  armature.  The  motor  armature  is 
held  from  rotating  in  the  reverse  direction  by  means  of  the  brake 
N,  Fig.  305.  A  train  coming  into  the  block  will  deenergize  the 


284 


RAILWAY  SIGNALING 


magnet  and  allow  the  blade  to  drop  to  the  caution  or  stop 
position. 

Two  governors,  0-0  fastened  to  the  armature  M,  revolve  with 
it  and  as  the  speed  increases  due  to  the  fall  of  the  blade,  the 
governors  swing  out  by  centrifugal  force  and  engage  against 
the  under  surface  of  I,  a  stationary  portion  of  the  hold-clear 
magnet.  The  tendency  of  the  blade  to  increase  its  speed  as  it 
falls,  serves  to  exert  a  pressure  by  the  governors  to  hold  it  in 
check. 

The  magnet  is  shown  partly  in  section  in  Fig.  304.  U  is  the 
winding  and  T  is  the  core.  The  core  is  fastened  to  an  outside 
shell  connected  with  the  insulated  piece  W,  the  bottom  of  which 
at  I  serves  as  a  friction  contact  for  the  governors,  0-0.  The 


FIG.  304. — Operating  mechanism  for  style  "K"  signal. 

brass  rings,  X,  serve  to  connect  the  terminals  of  the  magnet 
winding  with  the  outside  battery  through  two  brushes,  one  on 
each  ring.  In  order  to  prevent  such  injury  to  the  mechanism 
as  comes  from  stopping  suddenly,  there  is  a  ratchet  appliance  to 
permit  the  motor  to  continue  to  run  after  the  blade  comes  either 
to  the  caution  or  stop  position. 

176.  Hall  Style  "L"  Signal.— The  motors  of  the  Hall  Style  "L" 
signal  are  made  to  operate  on  either  8  or  110  volts  direct  current 
or  on  standard  voltages  and  frequencies  of  alternating  current. 
Figure  306  represents  the  top-post  mechanism  constructed  with 
direct-current  equipment.  The  motor  is  a  bi-polar  series  type 
operating  on  a  horizontal  axis.  Its  power  is  transferred  to  the 


SIGNAL  MECHANISM 


285 


signal  arm  through  a  train  of  gears  driven  by  a  small  pinion 
secured  to  the  motor  spindle  by  means  of  a  double  cone  slip 
clutch. 

The  hold-clear  mechanism  is  located  in  front  of  the  motor 
and  consists  of  a  latch  lever  in  which  is  a  spring  actuated  latch 
tfog  shown  in  (A),  Fig.  307. 
One  end  of  the  lever  is  piv- 
oted on  the  bearing  frame, 
and  the  lever  itself  is  free  to 
swing  downward.  As  the 
hold-clear  magnet  becomes 
energized  after  the  signal 
arm  comes  to  the  desired 
position,  its  armature  lifts 
the  latch  lever  until  the  latch 
dog  engages  with  one  of  the 
rollers  mounted  in  a  support 
flexibly  connected  to  the  outer 
end  of  the  motor  spindle.  This 
prevents  the  mechanism  from 
backing  up. 

The  controller  consists  of 
two  spindles  so  geared  to- 
gether that  when  they  are 
operated  by  the  pinion  that 
is  connected  to  the  main  gear 
spindle  they  will  move  sim- 
ultaneously. These  spindles 
carry  hubs  on  which  are 


mounted  contact  cams,  one 
of  which  is  shown  in  (B),  Fig. 
307.  A  snubber  is  provided 


FIG.    305.  —  Operating    mechanism 
style  "K"  signal. 


for 


to  relieve  the  shock  when  the  signal  arm  drops  to  the  45  and  0 
positions. 

177.  Federal  Three -position  Type  "4"  Signal.— The  Federal 
Type  "4"  signal  is  provided  with  an  electric  motor  of  suitable 
characteristics  to  adapt  it  for  use  on  direct  currents  of  varying 
potentials  from  8  to  110  volts  or  on  alternating  currents  of 
110  and  220  volts  with  the  usual  variation  in  frequency  which 
may  be  encountered. 

Figure  308  represents  a  10-volt  direct-current  top-post  mechan- 


286 


RAILWAY  SIGNALING 


R 


SIGNAL  MECHANISM 


287 


ism.     By  a  train  of  gears  the  motor  drives  the  blade  to  the  45- 
and   90-degree    positions.     When    the    semaphore    spindle   has 


FIG.  307. — Hold-clear  mechanism  and  circuit  controller  for  style  "L"  signal. 

reached  a  position  corresponding  to  proceed,  the  circuit  through 
the  motor  is  interrupted  and  a  circuit  through  the  hold-clear 


FIG.  308. — Federal  type  "4"  top-post  signal  mechanism. 

magnets    is    established.     The    hold-clear   magnet    for  10-volt 
direct-current  operation  is  generally  wound  to  a  resistance  of 


288  RAILWAY  SIGNALING 

500  ohms.  As  the  hold-clear  magnet,  DZ,  becomes  energized,  it 
attracts  the  armature  EJ  supported  by  the  arm  EF.  This  causes 
a  detent  roller  or  dog  to  engage  with  teeth  on  a  member  attached 
to  the  motor  shaft  in  such  a  manner  as  to  prevent  the  motor 
from  rotating  towards  the  stop  position,  as  long  as  current  flows 
through  the  hold-clear  coils. 

AUTOMATIC  STOPS 

178.  Motor-operated  Automatic  Stops. — The  motor-operated 
train-stop,  shown  in  Figs.  309  and  310,  was  designed  for  use  on 
lines  of  the  New  York  Municipal  Railway  Corporation  operating 
in  and  between  New  York  City  and  Brooklyn.     It  is  installed 
between  the  rails  of  the  track  and  is  operated  by  a  separate  tripper 
arm  through  the  medium  of  a  rocking  shaft  that  may  be  connected 
to  either  side  of  the  operating  mechanism.     The  trip  arms  are 
made  of  cast  iron  so  designed  that  they  will  break  if  any  unyielding 
portion  of  the  train  happens  to  strike  them,  but  not  when  the 
train  trip  arm  strikes  them.     The  circuit  breaker  is  operated 
directly  from  the  main  shaft  of  the  stop,  as  the  drawing  indicates. 

The  stops  on  these  lines  are  used  in  connection  with  all  signals 
except  dwarfs  at  interlocking  plants,  and  are  governed  by  the 
indication  of  the  signals.  When  a  signal  is  in  the  stop  position, 
the  tripper  arm  stands  above  the  rail;  and  if  a  train  attempts  to 
pass  the  signal  set  in  the  stop  position,  the  arm  engages  a  valve 
that  opens  the  air  line  on  the  train,  applies  the  brakes  and  stops 
the  train.  When  the  signal  is  clear,  the  arm  drops  below  the  top 
of  the  rail. 

LIGHT  SIGNALS 

179.  General. — Color-light   signals  are  built  for  long-  and 
medium-range  outdoor  service  and  for  short-range  indoor  service; 
while  position-light  signals  are  built  only  for  long-  and  short-range 
outdoor  service.     The  long-range  signals  are  used  for  high-speed 
trains  and  involve  considerable  accuracy  in  construction  and  in- 
stallation.    They  require  highly  concentrated  filament  lamps  for 
condensing  the  light  and  accurate  lenses  for  projecting  it.     As 
such  exacting  service  is  not  required  of  the  short-range  signals, 
their  construction  is  somewhat  simplified.     Concerning  long-range 
signals,  the  following  paragraphs  are  taken  from  the  1917  Pro- 
ceedings of  the  Railway  Signal  Association:1 

JPage  8. 


SIGNAL  MECHANISM 


19 


290 


RAILWAY  SIGNALING 


SIGNAL  MECHANISM  291 

"In  broad  daylight,  under  unfavorable  sun  and  background  condi- 
tions, there  are  two  alternatives  open  for  the  light  source:  Either  a 
very  high  wattage  lamp  must  be  used,  or  a  lower  wattage  with  a  con- 
centrated and  accurately  located  filament.  (As  illustrating  the  re- 
markable influence  of  concentrating  the  light  source,  we  refer  to  the 
April  and  May,  1914,  numbers  of  the  Signal  Engineer,  where  this  subject 
is  fully  treated.  Figure  24  shows  that  a  24-watt  concentrated  filament 
lamp  gives  a  peak  candlepower  of  65,000,  and  the  same  wattage  in 
commercial  lamp  gives  500  candlepower.  To  get  a  long-range  indica- 
tion, it  is  necessary  to  project  a  beam  candlepower  of  5,000  or  6,000.) 

"The  concentrated  filament  requires  an  accurate  basing  of  the  lamps 
so  that  they  may  be  interchanged  without  disturbing  the  alignment 
of  the  signal.  The  automobile  headlight  requires  refocusing  when  a  new 
lamp  is  put  in  place.  This  cannot  be  done  with  the  light  signal.  It 
would  involve  too  much  work  and  would  also  involve  the  employment 
of  two  experienced  men  to  take  care  of  realignment  whenever  a  lamp 
burned  out.  Moreover,  it  is  difficult,  if  not  impossible,  to  obtain  any 
very  accurate  adjustment  for  maximum  candlepower  in  the  field.  Such 
work  is  properly  done  in  a  dark  room.  The  lamps  for  high-speed  signals 
are,  therefore,  rebased  in  a  special  jig,  which  permits  the  accurate 
location  of  the  base  with  respect  to  the  filament. 

"If  a  commercial  concentrated  filament  lamp  were  to  be  used,  the 
diameter  of  the  filament  would  have  to  be  increased  to  allow  for  commer- 
cial variations  in  lamp  manufacture.  It  might  be  possible  to  design 
a  lamp  filament  having  sufficient  concentration  and  yet  having  area 
enough  to  permit  commercial  variations,  but,  as  these  commercial 
variations  permit  nearly  K-in.  departure  in  all  directions  from  a  theo- 
retical filament  location,  the  lamp  wattage  would  have  to  be  increased 
eight  or  nine  times  at  least  to  maintain  the  same  degree  of  concentration 
and  consequently  the  same  candlepower. 

"The  long-range  signal  has  a  very  small  beam  spread,  on  account  of 
the  concentrated  filament  employed.  Consequently,  these  signals  have 
been  designed  to  facilitate  accurate  alignment  by  providing  separate 
horizontal  and  vertical  adjustments.  When  it  is  still  necessary  to  provide 
some  means  of  increasing  the  spread  to  take  care  of  curved  track,  a 
prism  lens,  which  spreads  or  "fans"  the  light  in  the  horizontal  plane, 
but  which  does  not  increase  the  vertical  spread,  is  used,  and  the  light 
is  projected  in  the  most  efficient  manner  possible  (see  page  131  of  the 
May,  1914,  Signal  Engineer).  By  means  of  this  prism,  the  maximum 
possible  range  on  curved  track  is  secured  with  the  minimum  possible 
expenditure  of  power." 

COLOR-LIGHT  SIGNALS 

180.  Long-range  Type. — This  type  of  signal  is  used  principally 
on  steam  and  high-speed  electric  roads.  A  doublet  lens  is 


292 


RAILWAY  SIGNALING 


employed  *  in  order  to  utilize  to  better  advantage  the  rays  of 
light  from  the  lamp.  The  outer  lens  is  made  of  clear  glass  from 
8%  to  10  in.  diameter  with  approximately  4  in.  focal  length. 
The  inner  lens  is  colored  and  is  generally  5%  in-  m  diameter 
with  a  }4  m-  f°cal  length. 

Figure  311   shows  the  Union  Style  L,   three-position  long- 
range  colored-light  signal  installed  on  the  electrified  portion  of 


FIG.  311. — Front  and  back  views  of  Union  style  "L"  light  signal. 

the  C.  M.  &  St.  P.  R.  R.  The  range  of  vision  on  a  tangent 
varies  from  2,500  ft.  when  the  sun  is  shining  directly  on  the  lens 
to  4,000  ft.  under  more  favorable  conditions.  The  three  outer 
doublet  lenses,  each  8%  m-  in  diameter,  are  provided  with  an 
individual  hood  over  each  lens.  The  bottom  lens  gives  the  stop 
indication,  the  middle  one  caution,  and  the  top  proceed.  The 
main  lamps  for  lighting  signals  are  6-volt,  28-watt,  with  con- 


SIGNAL  MECHANISM 


293 


centrated  filament.  On  tangents,  lenses  having  a  spread  of  3 
degrees  were  used,  but  on  curves  deflecting  prisms  of  10  or  20 
degrees  were  used  depending  upon  the  amount  of  curvature  of 
the  track  and  the  length  of  view.  A  metal  background  extend- 
ing entirely  around  the  hood  was  provided  for  each  signal  to 
intensify  the  signal  indication. 

Figure  312  shows  a  double  light  signal  installed  on  the  Union 
Traction  Company  of  Indiana  by  the  General  Railway  Signal 
Company.  The  signals  governing  in  each  direction  are  mounted 


FIG.  312.— A.  P.  B.  light  signal. 

back  to  back  on  a  bracket  on  the  same  pole.  The  upper  case 
houses  the  red  and  green  lamps  and  the  lower  the  yellow  or 
permissive  lamp.  This  signal  is  used  in  the  "Absolute  Permissive 
Block  System,"  the  red  being  the  absolute  indication  for  opposing 
movements  and  the  combination  of  red  and  yellow  being  the 
permissive  indication  for  following  movements. 

181.  Medium-range  Outdoor  Type. — The  medium-range  sig- 
nal is  provided  with  a  simpler  lens,  generally  5%  in.  in  diameter. 
The  three-position  signal  shown  in  Fig.  313  is  lighted  with  two  36- 
watt  110-volt  tungsten  lamps  connected  in  multiple.  It  has  a 
range  of  vision  approximately  1,500  ft.  under  adverse  conditions 
of  sunlight  and  2,500  ft.  at  other  times.  The  design  is  compara- 


294 


RAILWAY  SIGNALING 


lively  simple  and  the  signal  is  used  on  medium-speed  interurban 
and  elevated  lines. 

Figure  315  is  a  detail  of  the  interlocking  signal  shown  in  Fig. 
314  and  used  on  the  subway  and  elevated  lines  of  the  New  York 
Municipal  Railway  Corporation.  The  signal  is  semi-automatic, 
lever-controlled,  and  has  two  pairs  of  lights  with  three  in  each 


FIG.  313. — Union  Model  "N"  light  signal.     Rear  view. 

pair  that  serve  the  same  purpose  as  a  two-arm  semaphore  signal. 
Five-in.  doublet  lenses  with  a  30-watt  lamp  behind  each  lens,  are 
used  on  the  elevated  lines.  The  subway  signal  is  an  exact  duplicate 
of  the  elevated  type,  except  that  a  plain  lens  and  a  10-volt  12-watt 
lamp  is  used.  An  emergency  signal  referred  to  as  a  calling-on 
signal  is  mounted  just  below  the  lower  lens  of  this  double  signal. 
When  this  calling-on  signal  is  displayed  the  words  "  Proceed  at 
Caution"  are  illuminated.  The  calling-on  signal  is  always 


SIGNAL  MECHANISM 


295, 


displayed  with  two  red  lights  showing  above  and  means  that  the 
motorman  is  to  press  the  emergency  pushbutton  located  on  the 
side  of  the  signal.  This  push-button  is  used  to  clear  the  stop 


Red 


Stop  and  Stay 
* 


Key  Automatic 
Stop.Proceed 

expecting  to  find  route  expecting 

Block  occupied  to  find  nex  t 


3  4 

Proceed  Caution  Proceed  Caution 
over  diverging      diverging  rou  te 
Automatic 
Block  Clear 
Signal  Red 

SEMI-AUTOMATIC    INTERLOCKING  SIGNAL 


'  Proceed  Caution 
over  main  route 


6 

Proceed 


expecting  to  find 
Signal  Red 


next  Si 


Green 
Yellow 
Red 


Stop,  Ke  y  Automatic  Stop       Proceed Cau  tion  expecting 
ana  Proceed  expecting  to  find  next  Signal  Red 

to  find  Block  occupied. 

AUTOMATIC   SIGNALS 


9 

Proceed 


Yellow 
Red 


10 
Stop  and  Stay 


Proceed  Caution 


INTERLOCKING  DWARF  SIGNALS 

FIG.  314. — Signals  used  on  lines  of  New  York  Municipal  Railway  Corporation. 
(General  Railway  Signal  Co.) 

in  case  of  an  emergency  when  the  signal  apparatus  fails  or  when 
it  becomes  necesary  to  use  the  calling-on  signal.  After  the 
motorman  clears  the  automatic  stop  he  proceeds  slowly  expecting 
to  find  the  block  occupied  or  to  cross  over  to  another  track  and 


296 


RAILWAY  SIGNALING 


Foundation  Plan 
FIG.  315. — Interlocking  signal  shown  in  Fig.  314. 


SIGNAL  MECHANISM 


29? 


move  against  the  normal  direction  of  traffic.  A  rear  home  signal 
is  used  on  these  lines  for  the  same  purpose  as  a  distant  semaphore 
signal.  It  is  a  standard  single  three-indication  signal,  semi- 


FRONT  VIEW 

FIG.  316. — Subway  and  tunnel  signal.      (Union  Switch  and  Signal  Co.) 

automatic  in  its  operation.     The  dwarf  signal  used  at  interlocking 
plants  is  a  non-automatic  two-indication  signal. 

182.  Short-range  Subway  and  Tunnel  Type. — Subway  and 
tunnel  signals  are  simple  in  design  since  there  is  no  need  of  protec- 


RAILWA  Y  SIGNALING 


(A)  Signal  lamps,  background  omitted. 


(B)  Details  of  signal  lamp. 
FIG.  317. — Position-light  signal.      (Union  Switch  and  Signal  Co.) 


SIGNAL  MECHANISM 


299 


tion  against  sunlight.  The  hood  is  unnecessary,  the  lenses  are 
small,  and  the  lights  require  less  current  than  the  outdoor  type. 
Figure  316  shows  the  type  of  signals  installed  in  the  Boyleston 
Street  Subway  of  the  Boston  Elevated  Railroad.  Each  lens  has 
behind  it  two  4-  c.p.  55-volt  tungsten  lamps. 


POSITION-LIGHT  SIGNALS 

183.  Long-range. — The  position-  or  beam-light  signals  have 
lenses  that  are  yellow  tinted.  The  range  of  vision  averages  about 
2,500  to  4,000  ft.  for  high-speed  signals  and  about  1,000  ft.  for 
dwarfs.  Of  the  three  rows  of  lights  shown  in  Fig.  317  represent- 


FIG.  318. — Position-light  dwarf  signal. 

ing  the  three  positions  of  the  upper  blades  in  upper  quadrant 
signaling,  only  one  can  be  illuminated  at  a  time.  The  selection 
is  done  by  a  three-position  relay  operating  in  the  same  manner  as 
for  a  semaphore  signal.  The  lights  in  the  lower  portion  of  the 
signal,  Fig.  319,  correspond  to  the  lower  blade  of  a  two-arm 
semaphore,  and  the  combination  of  the  two  sets  is  used  to  carry 
out  the  more  recent  aspect  scheme  of  the  Railway  Signal  Associa- 
tion for  block  signaling  and  interlocking.  The  four  12- volt 
5- watt  lamps  in  each  row  are  spaced  18  in.  on  centers  and  are 
equipped  with  5%-in.  inverted  toric  lenses,  as  shown  in  (B), 
Fig.  317.  The  same  voltage  is  used  for  both  day  and  night 
indications.  The  glass  reflector  placed  at  an  angle  just  above  the 
lamp  tends  to  throw  the  light  downwards  and  assists  in  giving 
a  good  short-range  indication.  Each  lens  is  covered  with  a 
deep  hood  to  protect  it  from  the  sunlight. 


300 


RAILWAY  SIGNALING 


SIGNAL  MECHANISM  301 

184.  Short-range  or  Dwarf. — The  dwarf  is  made  with  two 
lights  in  each  row  giving  the  three  indications  of  a  semaphore 
blade  in  upper  quadrant  signaling.  As  the  range  is  shorter,  the 
lenses  are  not  so  large  and  the  filament  adjustments  are  not  so 
accurate. 


CHAPTER  XVI 
HIGHWAY  CROSSING  SIGNALS 

185.  General. — In  these  days  of  extensive  highway  travel,  it 
has  become  the  practice  to  install  signals  at  grade  crossings  to 
give  warning  of  the  immediate  approach  of  trains.     This  has 
become  practically  a  necessity  since  the  advent  of  the  automobile, 
for  it  is  the  common  occurrence  now  for  persons  to  start  across 
country  on  an  overland  journey  of  hundreds  and  even  thousands 
of  miles  crossing  railroad  tracks  that  they  have  never  seen  nor 
heard  of  before.     It  was  different  in  earlier  days  when  all  such 
travel  was  by  buggy  or  wagon  where  one  seldom  went  more  than 
12  or  15  miles  from  home  and  knew  the  details  of  every  railroad 
crossing  within  that  section.     The  busiest  crossings  in  the  cities 
are  protected  by  flagman  and  by  gates;  but  it  is  impractical  to 
watch  every  crossing,  especially  those  in  outlying  and  country 
districts. 

Both  visible  and  audible  signals  have  been  installed  to  meet 
this  need.  The  visible  signals  are  constructed  with  a  plain 
light,  a  flash  light,  a  moving  light,  a  wigwag  arm,  or  combinations 
of  such  methods  of  giving  indications.  On  account  of  the 
increase  in  travel  by  automobile  and  motorcycle  with  their 
attending  noises,  the  visible  signal  seems  to  meet  the  requirement 
better.  Besides,  more  and  more  of  the  automobiles  are  made 
enclosed,  especially  for  winter  service.  The  audible  signal  is 
essentially  the  ringing  bell.  Many  manufacturers  are  making 
use  of  both  visible  and  audible  signals,  combining  them  in  one 
signal  for  both  day  and  night  indications. 

186.  Highway  Crossing  Signals. — Figure  320  represents  the 
Union     Three    Aspect    Automatic    Flagman.     When    a   train 
approaches  the  crossing  where  such  a  signal  is  installed,  the  red 
banner  swings  across  the  road  to  give  warning.     The  banner 
carries  a  red  light  and  has  the  letters  S-T-O-P  painted  across  the 
face  of  the  disc.     The  red  lamp  is  lighted  only  when  the  banner  is 
in  motion.     When  there  is  no  train  approaching  the  crossing, 
the  banner  is  concealed  between  the  two  metal  screens  which 

302 


HIGHWAY  CROSSING  SIGNALS 


303 


bear  the  words  "Look,"  "Listen."     On  top  of  the  post  is  a  gong 
type  of  bell  that  rings  while  the  banner  is  swinging. 


CLEAH  ASPECT 
H«d  Di«  Concealed 


STOP  ASPECT 
X«I  Disc  Stationary 


FIG.  320. — The  Union  three  aspect  automatic  flagman. 

The  operating  equipment  consists  chiefly  of  electro-magnets, 
two  pairs  of  which  are  operating  coils  that  swing  the  arm  and 
one  pair  is  a  set  of  holding  coils  that  retain  the  arm  between  the 
screens.  The  flagman  operates  on  a 
local  circuit  of  10  volts  direct  current 
requiring  0.4  amp.  to  swing  the  arm 
and  0.4  to  light  the  5-watt,  12-volt  lamp. 
The  holding  coils  are  wound  with  a  re- 
sistance of  1,000  ohms,  thereby  reducing 
to  a  minimum  the  amount  of  current 
consumed  while  the  signal  is  giving  the 
clear  indication.  The  lamp  attached  to 
the  banner  can  be  either  fixed  or  oscillat- 
ing. The  fixed  lamp  can  be  so  arranged 
with  an  oil  burner  as  to  give  flashes  of 
light  as  the  arm  swings  back  and  forth. 

Figure  321  is  a  highway  crossing  signal 
having  a  crossing  sign,  a  wigwag  signal, 
and  a  locomotive  type  of  bell.  The 
signal  gives  warning  by  ringing  the  bell 
and  by  waving  at  right  angles  to  the 
highway,  the  red  wigwag  disc,  which  is  26 
in.  in  diameter.  When  the  signal  is  in  FIG.  321.— Wigwag  cross- 
motion,  the  red  lamp  in  the  center  of  ing  signal.  (Railroad  Supply 
the  disc  and  the  words  "DANGER," 

"STOP,"  are  all  illuminated  both  day  and  night  to  intensify 
the  indication  in  giving  the  warning  of  an  approaching  train. 


304 


RAILWAY  SIGNALING 


The  bell  ringing  at  the  same  time  the  wigwag  is  active  is  an 
additional  means  of  calling  attention  to  the  movement  of  the 
train. 

Figure  322  shows  the  locomotive  bell.  The  operating  mechan- 
ism in  (A)  is  a  solenoid  electro-magnet.  As  the  magnet  becomes 
energized  when  a  train  approaches,  the  solenoid  armature  is 


FIG,  322. — Locomotive  types  of  crossing  bells.     (Railroad  Supply  Co.) 

drawn  downward  causing  the  hammer  to  strike  the  bell.  Just  as 
it  is  drawn  down  far  enough  to  make  the  hammer  strike,  the  current 
is  broken  by  the  snap-switch,  and  the  hammer  falls  by  gravity. 
When  the  armature  reaches  its  normal  position,  it  completes  the 
circuit  through  the  snap-switch  and  energizes  the  relay  to  ring 


HIGHWAY  CROSSING  SIGNALS 


305 


the  bell  again.  The  process  is  repeated  40  to  60  times  a  minute 
giving  as  many  blows  to  the  bell.  This  equipment  can  be  used 
only  with  direct  current. 

The  locomotive  bell  may  be  operated  also  by  a  motor  as  shown 
in  (B).  By  means  of  a  train  of  gears,  the  motor  drives  a  cam 
that  raises  and  lowers  a  weight  to  which  is  attached  the  bell 
hammer.  The  weight  simply  serves  to  give  regularity  to  the 
striking  of  the  bell.  The  motor  may  operate  on  either  direct 
or  alternating  current. 


L 


B* 

TD 

—  1  D  A-  Wigwag  Motor 

P*—  ~T    -i     0-        »         Lamps, 
H  _  H     C  -  A.  C.  Crossing  Bell 

...  ..    m  ^   •  "  !»  3       D-  Nnn-lnfarlarkmn  f?elau 

FIG.  323. — 110-volt    A.C.    wigwag    circuit. 

Co.) 


Double    track.      (Railroad  Supply 


187.  Highway  Crossing  Signal  Circuits. — Figure  323  shows  the 
wiring  for  operating  the  motor,  lights  and  bell  by  110-volt 
alternating  current.  The  relays  are  of  the  neutral  type  controlled 
by  simple  track  circuits.  The  approach  of  a  train  makes  back 
contact  with  the  relay  armature  and  completes  the  circuit  to 


FIG.  324. — Low  voltage  signal  circuit  for  double-track  line. 

operate  the  wigwag  and  the  bell.     The  wigwag  is  actuated  by  a 
motor  connected  to  it  through  a  train  of  gears. 

Figure  324  shows  the  wiring  for  operating  highway  crossing 
signals  by  low  voltage  on  a  double-track  line.  A  bonded  track 
section  with  ordinary  track  circuits  is  established  for  about  a 
half  mile  on  the  approach  side  of  each  track.  Insulated  joints 


306  RAILWAY  SIGNALING 

are  maintained  at  each  end  of  each  section.  Two  ordinary 
relays  would  meet  all  of  the  requirements,  but  an  interlocking 
relay  with  the  interlocking  device  removed  is  sometimes  more 
desirable,  for  it  is  equipped  with  better  connections  for  such 
service  and  occupies  less  space.  A  train  in  either  section,  A  or  B, 
will  shunt  the  relay  for  that  section  and  cause  the  signal  to 
operate  as  long  as  either  of  the  blocks  is  occupied.  As  soon  as  the 
train  moves  out  of  the  block,  the  relay  becomes  energized  again 
and  the  signal  resumes  its  normal  position.  A  train  backing  up 
towards  the  crossing  would  not  cause  the  signal  to  give  any 
indication  of  such  movement. 

In  the  case  of  single-track  operation,  the  block  on  each  side  of 
the  highway  crossing  must  be  bonded,  and  track  circuits  estab- 
lished, but  an  interlocking  relay  is  required  to  prevent  the  sig- 


A-  Wigwag  Mofor 

C~-Crossirig  Sell? 
P-  Interlocking  fte/cry 
£-  Local  Battery     * 
F-  Track  Battery 


FIG.  325. — Low  voltage  wigwag  circuit.     Single  track.      (Railroad  Supply  Co.) 

nal  from  giving  a  warning  indication  after  the  train  has  cleared 
the  crossing.  Figure  325  shows  the  wiring  for  a  single-track 
road. 

188.  Interlocking  Relay. — Figure  326  illustrates  the  operation 
of  one  type  of  interlocking  relay.  Neither  of  the  blocks  is 
occupied  and  both  track  relays  are  energized.  When  a  train 
enters  from  the  left  at  A,  relay  K  becomes  deenergized  and  its 
armature  drops  away  by  gravity..  The  arm  D  strikes  pawl  F, 
tilting  it  slightly  to  the  left,  while  finger  E  makes  back  contact 
with  M,  causing  the  signal  to  give  the  warning  indication. 
As  soon  as  the  front  of  the  train  crosses  the  insulated  joint  B, 
the  relay  L  becomes  deenergized  and  its  armature  drops.  It 
cannot  make  back  contact,  however,  at  N ,  for  the  arm  J  falls 
into  the  notch  /  on  the  other  side  of  pawl  F.  After  the  train 
has  cleared  the  crossing  the  relay  K  becomes  energized  again  and 


HIGHWAY  CROSSING  SIGNALS 


307 


the  signal  ceases  to  give  its  indication.  The  arm  J  is  still  held  by 
the  pawl  F.  As  soon  as  the  train  has  passed  the  insulated  joint 
C,  the  relay  L  becomes  energized  and  lifts  its  armature. 


FIG.  326. — Diagram  showing  operation  of  Union  interlocking  relay. 

Figure  327  represents  a  type  of  interlocking  relay  in  wnich  the 
interlocking  arms  form  a  part  of  the  operating  circuit.  The 
diagram  shows  the  operation  of  the  relay  as  a  train  passes  through 
the  two  track  circuit  sections.  In  (a),  the  track  circuits  AB  and 
BC  are  unoccupied  and  the  bell  circuit  is  open.  The  train  has 
entered  track  circuit  AB,  in  (6),  and  has  deenergized  the  magnet 


308 


RAILWAY  SIGNALING 


L.  The  armature  L-l  has  fallen  forward  causing  finger  L-2 
to  make  contact  with  M,  closing  the  circuit  and  ringing  the  bell. 
In  (c),  the  train  occupies  both  track  circuits  AB  and  BC.  It  has 
deenergized  the  relay  R  and  the  finger  R-2  has  fallen  upon  finger 
L-2.  In  (d),  the  train  occupies  track  section  BC.  The  relay  L 


HH 

Mr' 


Track  Circuit  A  B  and  B  C  unoccupied. 
Bell  Circuit  Open. 


4-rf- 


Fig.  1 


*  I 

^H>  T^  —  !  

i    c 

Train  has  entered  Track  Circuit  A 
B  Relay  Magnet  L.  De-energized 
Armature  L-l  causes  Contact 
Finger  L-2  to  make  Contact  with 
M  Bell  Circuit  Closed. 


Train  in  Track  Circuit  A  B  and  B  C 
(at  crossing)  Relay  Magnet  R 
De-energized  Contact  Finger  R-2 
Resting  on  L-2  Bell  Circuit  Closed 


M 


Train  in  Track  Circuit  B  C  Relay  Magnet  L  Ener- 
gized Contact  Finger  R-2  resting  on  L-2  Bell  Circuit 
Open.  When  Train  passes  out  of  Track  Circuit  B  C 
an  parts  normal  as  in  Fig.  1. 

Operation  similar  in  either  direction. 

FIG.  327. — Diagrams  a,  b,  c  and  d  showing  the  operation  of  style  "A"  universal 
crossing  bell  relay.     (Chicago  Railway  Signal  and  Supply  Co.) 

has  become  energized  again  and  its  armature  has  lifted  the  finger 
L-2  clear  of  contact  M.  This  action  has  opened  the  bell  circuit 
and  has  caused  the  bell  to  stop  ringing. 

189.  Hoeschen  Bell  System. — Figure  328  represents  a  Style 
"A"  selective  magneto-generator  for  the  Hoeschen  system  of 


HIGHWAY  CROSSING  SIGNALS 


309 


crossing  signals.  The  motive  power  used  to  operate  the  bell  is 
obtained  from  the  natural  spring  of  the  rail,  which  is  utilized  by 
means  of  levers  placed  under  the  base  of  the  rail.  An  illuminated 


FIG.  328. — Style  "A"  selective  magneto-generator.     Hoeschen  system. 

sign  that  remains  illuminated  only  while  the  bell  is  ringing  may  be 
used  also  to  give  additional  warning. 

Figure  329  shows  the  generator  with  the  cover  removed.     B 


FIG.  329. — Style  "A"  generator  with  cover  removed. 

represents  the  armature  at  rest  on  the  induction  coils,  C,  C, 
which  are  fastened  to  the  poles  of  a  group  of  three  permanent 
magnets,  D,  D;  E  represents  the  armature  rocker  tripping  pin, 


310 


RAILWAY  SIGNALING 


which  rests  on  the  upper  ends  of  the  two  vertical  rods  F  and  G. 
These  rods  are  supported  on  the  ends  of  scale  levers  0  and  S, 
which  are  termed  "operating"  and  l 'shunt,"  and  are  placed  in  a 
V-shaped  position  with  their  outer  ends  resting  firmly  against 


the  under  side  of  the  rail.  These  levers  being  fulcrumed  close 
to  the  rail  multiply  the  depressions  caused  by  a  passing  train.  As 
the  ratio  of  the  lever  arms  is  1  to  12,  a  depression  of  Jie  m-  gives 
the  inner  end  of  levers  0  and  S  an  upward  stroke  of  %  in.,  which 
is  sufficient  to  operate  or  shunt  the  generator  as  may  be  required. 


HIGHWAY  CROSSING  SIGNALS 


311 


K,  K  represent  the  housings  for  spiral  compression  springs  with 
plunger  resting  on  scale  levers  0  and  S  so  as  to  increase  or  decrease 
the  tension  of  these  levers.  Two  wires  lead  out  from  the  induc- 
tion coils  through  a  lightning  arrester  to  wires  PF,  W  and  thence 
to  the  bell.  SS  represent  heavy  springs  used  to  protect  the 
mechanism  from  excessive  vibration  caused  by  the  passing  trains. 

Figure  330  represents  a  dia- 
gram for  single-track  installation 
of  this  system.  Levers  0  and  S 
are  so  arranged  that  the  operat- 
ing lever  is  always  depressed 
slightly  in  advance  of  the  shunt 
lever  as  a  car  or  train,  moving 
towards  the  crossing,  passes  over 
the  track  opposite  the  generator. 
The  depression  of  the  operating 
lever  forces  the  vertical  rod  G  up- 
wards, thus  imparting  both  an 
upward  and  inward  motion  to 
the  armature  rocker  tripping 
pin  E.  This  brings  it  in  contact 
with  the  armature  B  with  suffi- 
cient force  to  separate  the  arma- 
ture quickly  from  the  poles  of  the 
induction  coils  C,  C,  thus  gener- 
ating a  momentary  current  of 
high  voltage  that  is  transmitted 
to  the  bell.  As  the  car  moves 
from  the  crossing,  the  shunt  lever 
is  depressed  in  advance  of  the 
operating  lever.  The  depression 
of  the  shunt  lever  forces  the  rod 
F  upwards,  imparting  both  an 
upward  and  an  outward  motion 

to  the  tripping  pin  E.  This  allows  the  pin  to  pass  the  end  of 
the  armature,  and  the  depression  of  the  operating  lever  imme- 
diately afterwards  has  no  actuating  effect. 

Figure  331  shows  the  motor  of  the  signal  equipped  for  single- 
track  operation  with  both  time  and  automatic  contact  attach- 
ments. The  motor  consists  of  a  simple  gear  movement  of  three 
wheels  used  in  connection  with  three  powerful  motor  springs. 


FIG.  331. — Details  of  Hoeschen  bell 
mechanism. 


312  RAILWAY  SIGNALING 

The  selective  generators  are  connected  in  series  with  the  releasing 
magnets,  M,  M,  by  separate  metallic  circuits  running  each  way 
from  the  crossing,  as  shown  in  Fig.  330.  Each  pair  of  releasing 
magnets  is  equipped  with  a  pointed  armature  N,  N,  and  both 
these  armatures  engage  the  releasing  clutch  lever  L.  This  lever  L 
engages  the  releasing  lever  RL  and  holds  it  as  shown  when  the 
motor  is  not  in  motion.  When  either  of  the  releasing  magnets 


FIG.  332. — Hoeschen  crossing  signal. 

is  energized  by  the  operation  of  the  selective  generator,  its 
armature  N  lifts  the  clutch  lever  L,  thus  releasing  the  motor 
through  the  lever  RL.  As  the  escapement  wheel  turns  from 
right  to  left,  it  imparts  a  rocking  motion  to  the  rocker  RR,  which 
is  connected  direct  by  rod  RO  to  a  pendulum  bell  hammer  that 
strikes  at  regular  intervals  the  inner  side  of  a  locomotive  type 
of  bell,  shown  in  Fig.  332. 

The  motor  is  provided  with  both  an  automatic  and  time 


HIGHWAY  CROSSING  SIGNALS  313 

stopping  device.  The  time  stopping  arrangement  operates  as 
follows:  When  a  motor  is  released  and  the  escapement  wheel 
starts  to  turn  from  right  to  left,  it  exerts  a  slight  pressure  on  a 
counterweight  that  is  fastened  to  the  inner  end  of  the  RL  lever 
shaft  directly  above  the  escapement  wheel.  This  movement 
forces  lever  RL  to  move  slightly  to  the  left,  where  it  is  locked  by 
the  latch  lever  F;  and  it  remains  in  this  position  until  released 
by  the  sliding  sawtooth  bar  XX.  As  each  revolution  of  the 
escapement  wheel  raises  this  bar  one  notch  or  tooth  by  means  of 
the  small  stud  On  the  hub  of  the  wheel,  it  raises  the  lever  F,  and 
allows  lever  RL  to  swing  back  to  normal  by  force  of  the  counter- 
weight, thus  stopping  the  motor. 

The  automatic  cut-out  or  stopping  mechanism  is  operated 
simultaneously  with  the  winding  of  the  motor  by  a  passing  train. 
The  slight  depression  of  the  rail  of  Hz  or  Jfe  m->  caused  by 
a  passing  train,  imparts  a  rocking  or  reciprocating  movement  to 
the  bell  crank  lever  resting  against  the  under  side  of  the  rail. 
This  motion  is  transmitted  by  a  connecting  rod  through  the 
rocker  plate  RP  to  the  two  winding  arms  WA  which  are  provided 
with  ratchet  dogs  on  the  inner  sides  that  actuate  the  ratchet 
wheel  and  wind  the  springs.  This  operation  imparts  the  recip- 
rocating motion  of  the  rod  AA  fastened  to  the  right  winding 
arm  WA  and  connected  by  friction  clutch  lever  FC  to  latch 
lever  F,  thus  releasing  the  RL  lever  and  allowing  it  to  move 
back  to  its  normal  position,  thereby  locking  the  escapement 
crank  and  stopping  the  motor. 

A  small  dial  with  a  pointer  is  shown  on  the  face  of  the  motor. 
This  indicates  to  the  signal  maintainer  the  amount  of  potential 
energy  stored  up  ready  for  service.  The  motor  is  always  nearly 
or  entirely  wound  and  provision  is  made  to  prevent  overwinding. 
When  fully  wound  it  will  deliver  about  20,000  strokes  on  the  bell 
and  will  run  continuously  for  an  hour  and  forty  minutes. 

Figure  333  shows  a  cross-sectional  view  of  the  Style  "S" 
magneto-generator,  a  newer  type  designed  to  meet  the  demands 
of  "safety  first."  The  mechanism  is  constructed  to  operate  by 
the  depression  of  the  rail  under  the  wheels  of  a  passing  train  in 
practically  the  same  manner  as  the  Style  "A"  generator.  The 
operation  of  the  generator  is  made  selective,  or  directional, 
by  the  use  of  a  selector  instrument  designed  along  the  same  gen- 
eral lines  as  the  generator.  It  is  installed  from  4  to  6  ft.  from 
the  generator  in  the  direction  from  which  no  operation  is  desired, 


314 


RAILWAY  SIGNALING 


HIGHWAY  CROSSING  SIGNALS 


315 


the  weight,  section  and  stiffness  of  the  rail  determining  the 
spacing  between  generator  and  selector.  The  instrument  con- 
sists of  a  simple  spring  switch  that  stands  normally  open  which  is 
connected  in  multiple  to  the  two  line  wires  running  from  the 
generator  to  the  bell.  A  car  or  train  going  from  the  bell  or  signal 
passes  over  the  selector,  causing  the  switch  to  close  by  means 
of  a  plunger  and  scale  lever  arranged  as  in  the  generator.  The 
selector  operates  a  fraction  of  a  second 
before  the  generator,  and  the  current  gen- 
erated by  the  operation  of  the  magneto  is 
shunted  out  from  the  line  by  the  closed 
switch  on  the  selector.  For  traffic  ap- 
proaching the  crossing  the  selector  remains 
unaffected,  with  its  shunt  switch  open,  until 
the  generator  has  operated,  thus  permitting 
a  closed  circuit  from  the  generator  to  the 
bell. 

190.  AGA  Highway  Danger  Signals.— 
Figure  334  illustrates  an  AGA  Highway 
Danger  Signal.  The  round  lamp  box  at 
the  top  is  30  in.  in  diameter  with  trans- 
parent letters  around  the  face  of  it  and  a 
flasher  in  the  center  behind  the  8%-in. 
red  spread-light  lens.  The  day  and  night 
indications  are  both  given  by  an  acetylene 
light  flashing  through  the  red  lens  and  the 
transparent  letters.  The  center  of  the 
lens  is  6%  ft.  above  the  concrete  foot- 
ing. The  entire  sign  is  made  of  cast 
iron.  The  lamp-box  rests  on  a  housing, 
which  contains  the  gas  cylinder,  high-  and 
low-pressure  equipment,  and  the  electro-gas  valve  when  the 
signal  is  used  as  a  railroad  crossing  sign. 

The  cylinder  is  filled  with  gas  to  a  pressure  of  150  Ib.  per 
square  inch  at  a  temperature  of  60°F.  From  the  cylinder,  the 
gas  flows  through  a  regulator  that  reduces  the  pressure  to  less 
than  1  Ib.  a  square  inch,  and  then  it  passes  on  to  the  flasher 
shown  in  Fig.  335.  After  the  gas  passes  through  the  pipe  B  of 
the  flasher  into  the  small  chamber  C,  a  part  of  it  goes  to  feed  the 
pilot  burner  D,  and  the  remainder  passes  through  opening  E 
into  the  gas  chamber  F.  After  enough  has  accumulated  in  this 


FIG.  334.— AGA   high- 
way danger  signal. 


316 


RAILWAY  SIGNALING 


chamber,  the  pressure  forces  the  diaphragm  G  downward  pulling 
with  it  the  lever  H  and  thereby  unseating  it  at  S.  The  gas 
escapes  through  the  passage  /  to  the  burner  K,  and  the  pilot  D 
ignites  it  to  produce  the  flash.  As  the  passage  S  is  much  larger 
than  the  opening  E,  the  gas  escapes  faster  than  it  enters;  and  as 
soon  as  the  pressure  drops  sufficiently,  the  diaphragm  and  lever 
return  to  their  original  position.  The  end  of  lever  H  is  magnet- 
ized to  eliminate  any  lag  in  opening  and  closing  the  passageway 
S.  The  frequency  of  the  flash  is  regulated  by  the  lever  L. 

When  used  as  a  highway  approach  signal,  where  it  stands  at 
the  side  of  the  highway,  possibly  300  ft.  from  the  crossing,  the 


FIG.  335. — AGA  signal  flasher. 

size  of  the  burner  is  %Q  ft.  and  gives  a  flash  during  one-tenth  of 
the  entire  frequency  cycle.  The  number  of  flashes  can  be  what- 
ever desired,  but  the  usual  practice  is  60  a  minute.  In  24  hours 
of  continuous  operation  the  signal  consumes  0.8  cu.  ft.  of  gas. 
When  placed  on  the  right-of-way  as  a  grade  crossing  signal, 
the  flow  of  gas  to  the  flasher  is  controlled  by  an  electro-gas  valve 
operated  in  connection  with  track  circuits,  so  that  the  signal 
flashes  only  while  a  train  immediately  approaches  the  crossing. 
The  size  of  the  burner  is  %  ft.  and  gives  a  flash  during  one-fourth 
of  the  frequency  cycle.  Outside  of  the  gas  consumed  by  the 
pilot,  which  is  0.3  cu.  ft.  in  24  hours,  the  total  amount  used  per 
day  varies  directly  with  the  amount  of  train  service ;  but  with  30 
trains  each  way  a  day,  allowing  three  minutes  for  each  movement, 


HIGHWAY  CROSSING  SIGNALS 


317 


the  gas  consumption  will  be  only  0.6  cu.  ft.  per  24  hours  including 
that  burned  by  the  pilot.  The  red  light  can  be  seen  in  daylight 
for  a  distance  of  600  ft. 

The  AGA  Company  has  another  signal,  Style  "B,"  which 
operates  in  connection  with  track  circuits,  that  has  two  lenses 
the  upper  one  of  which  gives  continuous  green  flashes,  except, 


FIG.  336. — AGA  two-color  highway  danger  signal. 

while  a  train  approaches  the  crossing,  when  they  are  red  as  before. 
This  type  of  signal  is  illustrated  by  Fig;  336.  When  a  train 
enters  the  lighting  track  circuit  the  electro-gas  valve  closes  the 
outlet  to  the  burner  in  the  top  lamp  and  opens  the  inlet  to  the 
burner  with  the  red  lens  giving  a  series  of  red  flashes.  As  soon 
as  the  train  passes  out  of  the  block,  however,  the  flashes  become 
green  again. 


APPENDIX  A 

RULES 

GOVERNING  THE  CONSTRUCTION,  MAINTENANCE  AND  OPERA- 
TION OF  INTERLOCKING  PLANTS1 

PRELIMINARY  REQUIREMENTS 

Section  1 — Indications  and  Aspects. — (a)  As  far  as  practicable,  a  uniform 
system  of  indication  and  aspects  must  be  used  for  each  operating  division. 
When  requested  every  railroad  company  operating  in  this  state  shall  submit 
plans  to  the  Commission  showing  the  system  of  indications  and  aspects  in 
use,  or  which  it  proposes  to  use  for  fixed  signaling  for  each  operating  division. 

(6)  If  changes  are  made  by  any  railroad  company  in  its  system  of  signal 
indications  and  aspects  on  any  operating  division  in  this  state  subsequent 
to  the  filing  of  plans,  it  shall  notify  the  Commission  accordingly. 

Sec.  2 — Plans  to  be  Submitted. —  (a)  Prior  to  the  construction,  reconstruc- 
tion or  rehabilitation  of  any  interlocking  plant,  there  shall  be  filed  with  the 
Commission  as  a  basis  for  approval,  the  following  plans  : 

(6)  A  station  map  or  other  plat,  drawn  to  scale,  showing  all  tracks,  bridges, 
buildings,  water  tanks,  and  other  physical  surroundings  located  on  the  right 
of  way  of  each  company. 

(c)  Profiles  showing  the  grade  of  each  railroad  company's  main  tracks  for  a 
distance  of  not  less  than  two  (2)  miles  in  each  direction  from  the  crossing  or 
junction. 

(d)  A  track  plan  in  duplicate  (and  as  many  more  as  the  roads  desire 
approved)  showing  the  location  of  all  interlocking  units,  the  tower  and  its 
general  dimensions,   and   any  other  appurtenances  necessary  to  show  a 
complete  layout  of  the  proposed  interlocking  plant.     When  not  expedient  to 
locate  accurately  all  physical  characteristics  by  figures,  they  should  be 
established  by  scaled  distances  within  the  interlocking  limits  hereinafter 
specified. 

(e)  When  merely  changes  and  additions  are  involved,  no  station  maps  or 
profiles  need  be  filed  with  the  track  plans  except  when  requested  by  the 
Commission. 

(/)  All  plans  filed  with  the  Commission  under  this  and  other  sections  must 
be  of  light  weight  paper  when  in  the  form  of  blue  prints. 

Sec.  3 — Symbols. — In  the  preparation  of  plans,  the  symbols  approved  by 
the  Railway  Signal  Association  shall  be  used  to  indicate  switches,  derails, 
signals  and  other  essential  parts  of  the  interlocking  plant. 

Sec.  4 — Limits  of  Interlocking  Plants. — The  interlocking  limits  are  defined 
by  the  home  or  dwarf  signals  situated  on  any  specified  track  and  located 
farthest  from  the  point  to  be  protected.  Any  appliances  operated  in 

1  Prepared  jointly  by  the  engineers  of  the  Railroad  Commission  of  Wisconsin,  the 
Railroad  &  Warehouse  Commission  of  Illinois,  the  Railroad  &  Warehouse  Commission  of 
Minnesota,  and  the  Public  Service  Commission  of  Indiana,  and  adopted  by  their  respec- 
tive commissions. 

318 


APPENDIX  319 

conjunction  with  the  interlocking  plant,  and  situated  beyond  the  limits 
herein  designated,  are  considered  as  auxiliaries. 

Sec.  5 — Approval  of  Plans. — (a)  When  possible,  the  railway  companies 
concerned  should  agree  on  the  plans  before  submitting  them  to  the  Com- 
mission. 

(b)  If  the  preliminary  plans  are  satisfactory,  or  if  in  the  judgment  of  the 
Commission    modifications    are    necessary,   the  plans  will  be   approved 
accordingly.     Of  the  plans  so  approved,  one  copy  will  be  retained  by  the 
Commission,  and  the  duplicate  returned  to  the  petitioning  company. 

(c)  The  approval  herein  described  will  stand  for  a  period  of  one  year.     If 
the  work  is  not  commenced  within  that  period,  a  new  approval  must  be 
obtained. 

Sec.  6 — Physical  Changes,  Reconstructions  and  Rehabilitation. — No 
interlocking  plant  shall  be  reconstructed  or  rehabilitated,  nor  shall  any 
change  be  made  in  the  locking  or  in  the  location  of  any  unit,  until  plans  have 
first  been  submitted  to  and  approved  by  the  Commision. 

Sec.  7 — Conditional  Service. — (a)  Upon  the  completion  of  any  work  on 
interlocking  plants  which  involves  changes  in  the  locking,  the  units  must  be 
connected  and  adjusted,  the  plant  placed  in  conditional  service  for  not  less 
than  twenty-four  (24)  hours,  and  remain  so  until  relieved  by  order  of  the 
Commission. 

(6)  When  minor  changes  are  made  in  locking  under  plans  previously 
approved  by  the  Commission,  it  will  not  be  necessary  to  place  the  plant 
in  conditional  service  prior  to  the  time  it  is  ready  for  inspection;  and  in 
cases  when  permission  is  received  from  the  Commission  in  advance,  the 
plant  may  be  placed  in  full  operation,  if  the  Commission  is  unable  to  inspect 
it  writhin  twenty-four  (24)  hours  after  it  is  ready  for  inspection. 

(c)  Conditional  service  is  hereby  interpreted  to  mean  that  all  units  and 
other  apparatus  involved  be  connected  and  operated  from  the  interlocking 
machine  in  the  tower.  All  trains  shall  come  to  a  stop  at  the  governing  home 
or  dwarf  signal  regardless  of  its  position  and  that  such  signal  shall  not  be 
operated  to  give  a  proceed  indication  until  after  the  train  has  made  the 
prescribed  stop. 

Sec.  8 — Petition  for  Inspection. — (a)  Prior  to  or  accompanying  the 
petition  for  inspection  of  completed  interlocking  plants,  the  following  de- 
tailed plans  will  be  required : 

(6)  A  track  plan  similar  to  the  one  referred  to  in  section  2,  showing  all 
tracks  and  interlocking  units  as  actually  constructed,  the  terminal  ends  of 
each  track  to  be  numbered  or  lettered  for  use  in  connection  with  the  manipu- 
lation sheet.  A  locking  sheet  and  dog  chart  showing  the  arrangement  of 
locking  in  the  machine  as  installed;  wiring  plans  showing  in  detail  all  circuits 
used  in  connection  with  the  plant;  a  manipulation  sheet  with  or  without 
track  diagrams  as  required  by  the  Commission,  showing  in  tabulated  form 
the  numbers  of  all  levers  necessary  to  be  manipulated  for  any  given  route 
designated  on  the  track  plan. 

(c)  A  suitable  framed  manipulation  chart  and  track  diagram  shall  be 
properly  placed  in  the  interlocking  tower.  The  terminal  ends  of  each  track 
on  this  chart  shall  be  numbered  or  lettered  to  correspond  with  the  track 
plans  above  mentioned. 


320  RAILWAY  SIGNALING 

(d)  The  petition  for  inspection  of  any  interlocking  plant,  when  possible, 
shall  give  three  (3)  days'  notice  in  advance  of  the  time  when  the  plant  will 
be  ready  for  inspection.     Upon  receipt  of  such  notice,  the  Commission  will 
endeavor  to  have  the  plant  inspected  within  three  (3)  days  after  receiving 
such  advice.     If  the  Commission  is  not  able  to  make  the  inspection  within 
the  time  specified,  it  will  authorize  the  railroad  company  in  charge  to  place 
the  plant  in  full  operation,  subject  to  future  inspection. 

(e)  If  upon  the  inspection  of  any  interlocking  plant  by  the  Commission,  it 
is  found  to  be  installed  in  accordance  with  the  approved  plans,  a  temporary 
permit  will  be  issued  to  the  railroad  company  in  charge,  pending  the  issuance 
of  formal  permits. 

REQUISITES  OF  INSTALLATION 

Sec.  9 — Type  of  Signals. — (a)  Except  when  approved  by  the  Commission, 
all  interlocking  signals  must  be  of  the  semaphore  type.  The  apparatus 
connected  with  the  operation  of  these  signals  must  be  so  constructed  that  the 
failure  of  any  part  directly  controlling  the  signal  will  cause  it  to  display  its 
least  favorable  indication. 

(&)  Semaphore  arms  must  display  indications  to  the  right  of  the  signal 
post,  except  where  the  physical  conditions  on  a  road  require  the  display  of 
signal  indications  to  the  left. 

Sec.  10 — Location  of  Signals. — (a)  All  fixed  signals  must  be  located 
either  over  or  upon  the  right  and  next  to  the  track  over  which  train  move- 
ments are  governed,  except  on  roads  operating  trains  with  the  current  of 
traffic  to  the  left,  or  where  physical  conditions  require  placing  the  signals 
to  the  left  of  the  track. 

(6)  Bracket  post  signals  may  be  used  on  roads  operating  trains  over  two 
(2)  or  more  tracks  in  the  same  direction,  when  such  practice  is  uniform  for 
any  specified  operating  division,  or  where  local  conditions  require  their  use. 

Sec.  11 — Locking  of  Signals. — The  locking  between  the  levers  of  the  in- 
terlocking machine  must  be  arranged  so  that  a  home  or  dwarf  signal  cannot 
be  cleared  for  any  given  route  unless  all  switches,  derails,  movable  point 
frogs  and  other  units  in  the  route  are  in  proper  position  and  locked. 

Sec.  12 — Home  Signals. — (a)  When  required  by  the  Commission,  all 
home  signals  must  be  equipped  with  not  less  than  two  arms.  Unless 
operated  by  power  all  home  signals  in  mechanical  plants  must  be  pipe  con- 
nected except  when  otherwise  approved  by  the  Commission. 

(6)  When  used  in  connection  with  automatic  train  stopping  devices,  the 
home  signal  may  be  located  immediately  opposite  the  means  for  controlling 
the  apparatus  of  the  train  stopping  device. 

(c)  When  used  in  connection  with  derails  and  other  units  the  home  signal 
must  be  located  as  far  in  advance  of  such  units  as  is  necessary  to  secure  full 
protection,  but  in  no  case  shall  it  be  less  than  five  (5)  feet  in  advance  of  such 
units. 

(d)  When  home  signals  are  semi-automatic,  or  form  a  part  of  an  auto- 
matic block  signal  system,  calling-on-arms  or  some  other  means  may  be 
used  for  advancing  trains. 

(e)  All  high  speed  signals  located  in   automatic   block   signal    territory 
shall  be  semi-automatic  and  form  a  part  of  the  block  signal  system. 


APPENDIX  321 

Sec.  13 — Dwarf  Signals. — Dwarf  signals  indicate  slow  speed  movements 
and  may  be  used  to  govern  train  movements  on  all  tracks  other  than 
main  tracks,  except  as  hereinafter  specified;  on  main  tracks  to  govern  train 
movements  against  current  of  traffic,  and  when  approved  by  the  Commis- 
sion as  intervening  signals  to  facilitate  switching  movements.  When  used 
they  must  be  located  and  connected  in  the  same  manner  as  home  signals. 

Sec.  14 — Advance  Signals. — Advance  signals  may  be  used  when  neces- 
sary, and  must  be  installed  in  the  same  manner  as  home  signals. 

Sec.  15 — Distant  Signals. — (a)  On  level  and  ascending  grades,  distant 
signals  shall  be  located  not  less  than  two  thousand  five  hundred  (2,500)  feet 
in  advance  of  their  respective  home  signals.  On  descending  grades  the 
minimum  distance  of  two  thousand  five  hundred  (2,500)  feet  shall  be  in- 
creased at  the  rate  of  one  hundred  (100)  feet  for  each  one-tenth  (l-10th)  of 
one  per  cent  of  gradient. 

(6)  Where  conditions  justify,  the  location  and  character  of  distant  signals 
or  the  method  of  operation  may  be  varied  or  the  signals  be  omitted,  depend- 
ing upon  the  conditions  surrounding  each  particular  case. 

(c)  Except  as  hereinafter  provided,  all  high  speed  tracks  must  be  equipped 
with  power-operated  distant  signals  having  electric  locks  or  other  suitable 
apparatus  to  prevent  changing  of  the  route  until  such  signals  have  indicated 
their  normal  position. 

(d)  When  required  by  the  Commission,  distant  signals  shall  be  so  arranged 
as  automatically  to  indicate  stop  when  the  track  between  the  home  and 
distant  signals  is  occupied,  or  when  any  intervening  switch  is  not  in  its 
normal  position. 

Sec.  16 — Switches. — All  switches,  derails,  movable  point  frogs  and  other 
units  within  the  interlocking  limits  hereinbefore  defined  must  be  incorpor- 
ated in  the  plant. 

Sec.  17 — Derails  on  Steam  Roads. — (a)  Main  Tracks:  On  level  grades 
facing  derails  must  be  located  not  less  than  five  hundred  (500)  feet  from  a 
drawbridge  or  the  fouling  point  of  a  crossing  or  junction.  On  descending 
grades  facing  derails  must  be  located  to  give  practically  the  same  measure 
of  protection  as  for  level  grades,  and  the  minimum  distance  of  five  hundred 
(500)  feet  must  be  increased  at  the  rate  of  ten  (10)  feet  for  each  one-tenth 
(l-10th)  of  one  per  cent  gradient.  On  ascending  grades  the  minimum 
distance  of  five  hundred  (500)  feet  may  be  reduced  at  the  rate  of  ten  (10) 
feet  for  each  one-tenth  of  one  per  cent  gradient;  but  in  no  case  shall  such 
derails  be  located  less  than  four  hundred  (400)  feet  from  a  drawbridge  or 
the  fouling  point  of  a  crossing  or  junction. 

(6)  Pocket  Derails:  Where  such  are  used  they  shall  be  located  so  as  to 
derail  the  first  pair  of  wheels  on  the  ties  at  a  point  not  less  than  fifty  (50) 
feet  from  the  fouling  point  of  a  crossing  or  junction. 

(c)  Back-up  Derails:  These  shall  be  placed  not  less  than  two  hundred 
fifty  (250)  feet  from  a  drawbridge  or  the  fouling  point  of  a  crossing  or 
junction. 

(d)  Secondary  Tracks :  All  tracks  other  than  main  tracks  shall  be  termed 
secondary  tracks.     On  such  tracks  derails  shall  be  placed  not  less  than  two 
hundred  (200)  feet  from  a  drawbridge  or  from  the  fouling  point  of  a  crossing; 
and  not  Jess  than  fifty  (50)  feet  from  the  fouling  point  of  a  junction. 

21 


322  RAILWAY  SIGNALING 

(e)  The  fouling  point  is  where  two  trains  moving  toward  a  common  center 
would  come  in  contact. 

(/)  Where  conditions  justify,  the  location  of  derails  may  be  varied  or  they 
may  be  omitted,  when  approved  by  the  Commission. 

Sec.  18 — Derails  on  Electric  Roads. — The  location  of  derails  on  electric 
roads  shall  be  determined  in  the  same  manner  as  for  steam  roads.  In 
placing  derails  in  the  tracks  of  such  roads,  consideration  will  be  given  to 
speed  and  character  of  traffic. 

Sec.  19 — Type  of  Derails. — Derails  must  be  of  an  approved  pattern, 
suitable  for  the  purposes  intended  and  so  placed  with  reference  to  curvature, 
bridges  and  other  tracks  as  to  secure  a  maximum  of  efficiency  and  safety. 

Sec.  20 — Guard  Rails. — Where  physical  conditions  require  their  use, 
guard  rails  shall  be  installed  in  connection  with  derails.  When  used,  they 
shall  be  placed  between  the  track  rails,  parallel  to  and  not  less  than  ten  (10) 
inches  distant  in  the  clear  therefrom,  and  must  be  of  sufficient  height,  length 
and  strength,  and  be  properly  secured  to  the  track  ties. 

Sec.  21 — Automatic  Train  Control. — Automatic  train  stopping  devices 
which  are  a  part  of  a  system  of  automatic  train  control  approved  by  the 
Commission,  may  be  used  in  lieu  of  derails.  In  such  devices,  the  means  for 
automatically  applying  the  train  brakes  shall  be  located  a  sufficient  distance 
in  advance  of  the  fouling  point  as  to  insure  a  safe  braking  distance. 

Sec.  22 — Locks. — (a)  In  mechanical  plants  all  facing  switches,  split  point 
derails  in  main  tracks  and  all  slip  switches  and  movable  point  frogs,  must  be 
locked  with  facing  point  locks.  All  other  derails,  switches  and  other  units 
must  be  locked  either  with  facing  point  locks  or  with  switch  and  lock 
movements. 

(6)  In  plants  equipped  with  mechanical  signals,  all  derails  must  be  pro- 
vided with  bolt  locks;  also  all  switches,  movable  point  frogs  and  other  units, 
where  conditions  require  them. 

(c)  In  power  plants,  the  arrangement  must  be  such  that  the  signals 
operating  in  connection  with  derails,  facing  point  switches  and  other  units 
cannot  be  operated  unless  these  units  are  in  proper  position. 

Sec.  23 — Detector  Bars. — (a)  Unless  otherwise  provided,  all  derails, 
switches,  movable  point  frogs  and  other  units  shall  be  equipped  with  detector 
bars  of  approved  design  not  less  than  fifty-three  (53)  feet  in  length,  or  longer 
if  required. 

(6)  Except  as  hereinafter  provided,  all  crossings  shall  be  equipped  with 
detector  bars  of  suitable  length,  so  interlocked  as  to  insure  a  clear  crossing 
before  an  opposing  route  can  be  set  up  or  a  proceed  signal  given. 

(c)  Crossing  detector  bars  will  not  be  required  where  electric  locking  is 
installed;  nor  at  outlying  crossings  of  simple  character  where  no  switching 
is  performed,  when  the  plant  is  equipped  with  time  locks. 

Sec.  24 — Time  Locks. — Unless  equipped  with  electric  locking,  time  locks 
must  be  installed  to  prevent  the  changing  of  high  speed  routes,  until  after 
the  home  signal  has  displayed  the  stop  indication  a  predetermined  time. 

Sec.  25 — Electric  Locking. — Electric  locking  may  be  provided  in  place 
of  time  locks  and  crossing  bars.  When  used,  the  circuits  must  be  arranged 
so  as  to  prevent  the  changing  of  a  route  until  the  train  has  passed  through 
the  interlocking  limits  or  through  a  predetermined  part  of  the  plant. 


APPENDIX  323 

Sec.  26 — Detector  Circuits. — When  a  railway  company  is  equipped  with 
sufficient  maintenance  forces  for  properly  maintaining  electric  detector 
circuits,  such  circuits  may  be  used  in  place  of  mechanical  detector  bars. 

Sec.  27 — Machines. — (a)  All  mechanical  interlocking  machines  shall  be 
equipped  with  locking  of  the  preliminary  type. 

(6)  All  power  interlocking  machines  shall  have  the  locking  so  arranged 
as  to  be  effective  before  the  operating  conditions  of  any  circuit  directly 
controlling  a  unit  can  be  changed.  Suitable  indicating  and  locking  ap- 
paratus shall  be  provided  to  prevent  the  placing  of  a  lever  in  complete  normal 
or  reverse  position  until  the  unit  controlled  has  completed  the  intended 
operation,  except  that  signals  shall  indicate  the  normal  position  only. 

Sec.  28 — Locking  of  Levers. — (a)  The  locking  must  be  so  arranged  that 
conflicting  routes  cannot  be  given  at  any  stage  in  the  setting  up  of  a  route, 
nor  a  proceed  indication  given  until  all  switches,  derails,  movable  point 
frogs,  facing  point  locks  and  other  units  in  the  route  affected  are  in  proper 
position. 

(6)  When  a  separate  lever  is  used  to  operate  distant  signals  the  locking 
between  the  home  and  distant  signals  shall  be  so  arranged  as  to  prevent  the 
distant  signals  from  giving  the  proceed  indication  until  the  home  signals 
operating  in  connection  with  such  distant  signals  are  in  the  proceed  position. 

Sec.  29 — Locks  and  Seals. — (a)  All  interlocking  machines  must,  when 
practicable,  be  provided  with  means  for  locking  or  sealing  the  mechanical 
locking  and  indication  apparatus  in  such  a  manner  as  to  prevent  access  to 
any  except  authorized  employes. 

(6)  All  power  interlocking  cabinets,  time  locks,  time  releases,  emergency 
switches,  indicator  and  relay  cases  must  be  provided  with  suitable  covers 
and  fastenings  and  be  properly  sealed  or  locked,  and  must  not  be  opened  by 
any  but  authorized  employes. 

Sec.  30 — Cross  Protection. — (a)  As  far  as  practicable,  cross  protection 
apparatus  must  be  provided  in  connection  with  electric  interlocking  plants 
to  prevent  the  operation  of  any  unit  by  cross  or  grounds. 

(6)  Low  voltage  circuits,  as  far  as  practicable,  must  be  designed  to  prevent 
the  operation  of  apparatus  by  cross  or  grounds. 

Sec.  31 — Annunciators. — When  operating  conditions  require  annun- 
ciators, they  shall  be  installed. 

Sec.  32 — Signal  Towers. — (a)  Signal  towers  shall  be  so  placed  and  be  of 
such  height  and  size  as  to  best  serve  the  purpose  for  which  they  are  intended. 

(6)  The  use  of  interlocking  towers  for  purposes  other  than  interlocking, 
dispatching  and  block  work  is  undesirable. 

(c)  If  work  other  than  interlocking  is  carried  on  in  the  tower,  a  suitable 
partition  or  railing  must  be  provided  to  prevent  outsiders  from  having 
access  to  interlocking  apparatus,  and  interfering  with  the  duties  of  the  opera- 
tor or  towerman. 

Sec.  33 — Tower  Lights. — The  tower  lights  must  be  screened  off  so  that 
they  cannot  be  mistaken  for  signals  exhibited  to  control  train  movements. 

Sec.  34 — Material  and  Workmanship. — Material  and  workmanship  must 
be  first-class  throughout.  When  complete,  the  interlocking  plant  must  be 
in  every  way  suitable  and  sufficient  for  the  purposes  intended. 


324  RAILWAY  SIGNALING 

MAINTENANCE  AND  OPERATION 

Sec.  35 — Maintenance  and  Operation. — (a)  Interlocking  plants  must  at  all 
times  be  properly  maintained  and  efficiently  operated.  Any  rules  or  regula- 
tions that  the  railway  companies  may  have  adopted  for  the  guidance  of 
employes  in  operating  and  maintaining  interlocking  plants  must  be  appro- 
priately framed  and  conveniently  placed  in  interlocking  towers. 

(6)  When  an  interlocking  plant  is  taken  out  of  service  the  Commission 
must  be  notified  immediately.  Under  such  circumstances  train  movements 
must  not  be  governed  by  interlocking  signals  but  by  the  usual  precautions 
prescribed  by  statute  governing  train  movements  over  and  across  railway 
grade  crossings,  junctions  and  drawbridges. 

Sec.  36 — Interlocking  Reports. — Reports  for  each  interlocking  plant  shall 
be  filed  with  the  Commission  by  each  railroad  company  concerned,  which 
reports  must  be  filed  in  manner  and  form  prescribed  by  the  Commission. 


APPENDIX  B 

PART  I 
SIGNAL  ASPECTS 

The  following  memorandum  on  the  essentials  of  signaling, 
incorporated  in  the  report  of  the  Committee  on  Transportation  of 
the  American  Railway  Association,  May,  1911,  is  copied  from 
the  Manual  of  the  Railway  Signal  Association: 

"The  reports  of  various  Committees  of  the  Railway  Signal  Associa- 
tion and  of  the  American  Railway  Engineering  Association  on  the  subject 
of  signaling  have  been  submitted  to  this  Committee,  with  the  request 
that  the  essentials  of  signaling  be  outlined  or  defined  for  the  future  guidance 
of  their  Committees. 

The  subject  has  been  carefully  analyzed  and  considered.  There  are 
three  signals  that  are  essential  in  operation  and  therefore  fundamental,  viz: 

(1)  Stop. 

(3)  Proceed  with  caution. 

(3)  Proceed. 

The  fundamental,  "proceed  with  caution,"  may  be  used  with  the  same 
aspect  to  govern  any  cautionary  movement;  for  example,  when: 

(a)  Next  signal  is  "stop." 

(b)  Next  signal  is  "proceed  at  low  speed." 

(c)  Next  signal  is  "proceed  at  medium  speed." 

(d)  A  train  is  in  the  block. 

(e)  There  may  be  an  obstruction  ahead. 

There  are  two  additional  indications  which  may  be  used  where  movements 
are  to  be  made  at  a  restricted  speed,  viz: 

(4)  Proceed  at  low  speed. 

(5)  Proceed  at  medium  speed. 

Where  automatic  block  system  rules  are  in  effect,  a  special  mark  of 
some  distinctive  character  should  be  applied  at  the  stop  signal. 
The  Committee  therefore  recommends: 

Signal  Fundamentals 

(1)  Stop. 

(2)  Proceed  with  caution. 

(3)  Proceed. 

Supplementary  Indications  to  be  Used  Where  Required 

(4)  Proceed  at  low  speed. 

(5)  Proceed  at  medium  speed. 

Stop  signals  operated  under  automatic  block  system  rules  should  be 
designated  by  some  distinctive  mark  to  be  determined  by  each  road  in 
accordance  with  local  requirements." 

325 


326  RAILWAY  SIGNALING 

Recommendations  of  Committee  I 

Your  Committee  submits  for  approval  the  following  two  schemes  of 
signaling  in  conformity  with  the  recommendations  of  the  Committee  on 
Transportation. 

Scheme  No.  1 

FUNDAMENTALS 


1.  Si-op 

2.  Proceed  wffh  Caution 

3.  Proceed 


r 


rf 


As  means  of  designating  stop  signals  operated  under  automatic  block 
system  rules,  the  following  are  suggested : 

1.  The  use  of  a  number  plate;  or 

2.  The  use  of  a  red  marker  light  below  and  to  the  left  of  the  active  light;  or 

3.  The  use  of  a  pointed  blade,  the  blades  of  other  signals  giving  the  stop 
indication  having  square  ends;  or 

4.  A  combination  of  these  distinguishing  features. 


Scheme  No.  2 


4  -  Proceed  err 
t.-Stop  I — ,  Low  Speed 


2r  Proceed  5 -Proceed  at 

with  Caution  H  Medium  Speed 


3-Proceect 


a 


As  means  of  designating  stop  signals  operated  under  automatic  block  sys- 
tem rules,  the  following  are  suggested : 

1.  The  use  of  a  number  plate;  or 

2.  The  use  of  a  red  marker  light  below  and  to  the  left  of  the  active  light;  or 

3.  The  use  of  a  pointed  blade,  the  blades  of  other  signals  giving  the  stop 
indication  having  square  ends;  or 

4.  A  combination  of  these  distinguishing  features. 

Having  in  view  the  practice  of  indicating  diverging  routes  by  several  arms 
on  the  same  mast,  the  Committee  submits  for  approval  the  following  to 
establish  uniformity  in  this  practice: 


APPENDIX 


327 


Scheme  No.  3 


/.  Stop 


HI 
ID 


2    Proceed  with  Caution 


3    Proceed 


4    Proceed  with  Caution  on  the  Low-Speed  Route 


U  or 


J] 


5.    Proceed  on  the  Low  Speed  Kbufff 


r 


or          or 


6     Proceed  w'lth  Caution  on  Medium -speed  Route 


7.     Proceed  on  the  Medium-Speed  Route 


8.    Reduce  to  Medium  Speed 


328  RAILWAY  SIGNALING 

As  means  of  designating  stop  signals  operated  under  automatic  block 
system  rules,  the  following  are  suggested : 

1.  The  use  of  a  number  plate;  or 

2.  The  use  of  a  red  marker  light  below  and  to  the  left  of  the  active  light; 
or 

3.  The  use  of  a  pointed  blade,  the  blades  of  other  signals  giving  the  stop 
indication  having  square  ends;  or 

4.  A  combination  of  these  distinguishing  features. 

The  above  three  schemes  are  submitted,  after  an  earnest  effort  to  carry  out 
the  Committee's  instructions  to  submit  a  uniform  scheme  of  signaling,  with 
the  idea  that  each  scheme  is  complete  in  itself. 


PART  II 
SYMBOLS 

The  following  plates,  1-13,  are  symbols  recommended 

by  the  Railway  Signal  Association  for  use 

in  railway  signal  practice. 


330 


RAILWAY  SIGNALING 


NON-  AUTOMATIC. 

SEMI  -AUTOMATIC. 

SPECIAL 

r 

(POWER.) 

A   rvfM 

Resumes 

ME      ICM 

POWER 

(MECN.) 

STICK 

NON-STICK 

(POWER) 

/*" 

r---j 

ti 

> 

tn 

to 

h-  3 

fffl 

t 

i       1 

;     2 

:     3 

;    4 

;    s 

i     e 

S       7 

Two 
POSITION 
SIGNALING. 

2  -POSITION. 
OT060-OT070 
OT075-OT090 

j.I".13 
i     A 

Al 

Hi 

A3 

g 

tl 
n 

=1 

A6 

3D 

A7 

2-  POSITION. 

hn 

tn 

tn 

-n 

irn 

tn 

hn 

h$1 

OTOSO 

;     B 

Bl 

B2 

B3 

IB4 

65 

f~B6 

s 

2-  POSITION. 

h^i 

tea 

Ka 

ta 

bsg 

S 

153 

SI 

THREE 

Pntmnu 

OT04S 

i     c 

Cl 

C2 

C3 

|C4 

cs 

C6 

C7 

SIGNALING. 

2-  POSITION. 

.  //> 

tXx 

l/^ 

H^ 

yf> 

h€ 

\/P 

^> 

45  TO  90 

*^\^// 

f\r 

i^\lr 

I^Hr^ 

|\jp' 

:     o 

1     01 

1     02 

I     03 

1     04 

106 

D7 

3-  POSITION. 

JX) 

tea 

I3 

Si 

lE3 

|R 

3 

1^3 

bag 

0  TO  45  TO  90 

i     E 

rr 

EZ 

E3 

i     E4 

!   es 

1     E6 

r77 

NOTE:  ARMS  SHOULD  ALWAYS  BE  SHOWN  IN  NORMAL  POSITION. 

hjjjjj    SPECIAL  -  3  POSITION   NON-AUTOMATIC  ,  0  TO  45  . 
JE24                                  SEMI-AUTOMATIC  STICK  ,  45  TO  90  . 

jg^l    SPECIAL-  3  POSITION  NON-AUTOMATIC,  OT045. 

|E25                                 SEMI  -AUTOMATIC  NON-STICK 

,  45  TO  90. 

j      1    ABSOLUTE   STOP  SIGNAL.            j     <   DISTANT 

SIGNAL. 

!     ^   PERMISSIVE   STOP  SIGNAL.           }     T  TRAIN  ORDER  SIGNAL. 

ENDS   OF  BLADES  IN  SYMBOLS  ARE  TO  BE  OF  THE  ACTUAL  FORMS  USED  BY  THE 

ROAD  CONCERNED.  <P  NOT  SPECIFIED  THE  ABOVE  FORMS  WILL  BE  USED  ON  PLANS. 

U^13  FttFO  ARM. 

• 

tlirJ  UppfR  QUADRANT  SIGNAL. 

ii 

i^i-  1  j-  ' 

4      4 

44 

"4"4 

i 

\   rf 

,' 

I 

£l".Ij    LOW0*  RUADRANT   SIGNAL. 

n, 

j  £ 

* 

i 

S      / 

'/3« 

\ 

Yl 
\       1   YERTIOAL  ^                             JL 

K 

V3 

SO                     S  MARKER  LIGHTS.     DIAGRAMS  OF  PROPORTIONS  FOR  MAK- 

~~j  STAGGERED)                             "^  SYMBOLS  FOR  SIGNAL  BLADES  . 

o; 

PLATE  I. 


APPENDIX 


331 


GROUND 
MAST. 


GROUND  MAST  WITH 
BRACKET  ATTACHMENT. 


OFFSET 
BRACKET   POST. 


T 

BRACKET 
POST. 


SUSPENDED 
MAST. 


RING  ENCLOSED 
CHARACTERISTICS 

MEAN   U6HT  SlGNAl 
ONLY. 


POT  SIGNAL. 


SMASH   SIGNAL 


Disc  SIGNALS. 

(©)       (0) 


HOME  HOME  DISTANT         DISTANT         DOUBLE 

PROCEED.          STOP.  PROCEED.        CAUTION.      FUNCTIONED. 


PRESENT  SIGNAL  TO  BE  REMOVED. 


PRESENT  SIGNAL  TO  REMAIN. 


RELATION  OF  THE  SIGNAL  TO  THE  TRACK  AND  THE  DIRECTION  OF  TRAFFIC 

n 


"*      RIGHT  HAND  LOCATIONS. 


Ri6HT   HAND  SIGNAL. 


LEFT  HAND  SIGNAL. 


LEFT  HAND   LOCATIONS. 


RIGHT  HAND  SIGHAL 


LEFT  HAND  SIGNAL. 


PLATE  II. 


332  RAILWAY  SIGNALING 


INSULATING  RAIL  JOINTS. 


TRACK  CIRCUITS  IN  TRACK  CIRCUIT  ON  LEFT,  TRACK  CIRCUIT  ON  RIGHT, 

BOTH  DIRECTIONS.  NONE  ON  RIGHT.  NONE  ON  LEFT. 


|        |  ffiBI  EIBBIJ      TRAFFIC  DIRECTION 

STATION.  SIGNAL         SIGNAL  SUBSTATION  .  CROSSING  GATE. 

^STATION. 


)         I        )*|x|x| 


SIGNAL  BRIDGE.  GIRDER.  TRUSS.  TRESTLE. 

NOTE:  STATE  WHETHER  DECK,  HALF-THROUGH  OR  THROUGH  BRIDGE. 


LIFT  SPAN  .         BASCULE,  DOUBLE  LEAF.    BASCULE,  SINGLE  LEAF.       DRAW  SPAN  . 

.         ,    .  HIGHWAY  CROSSINGS. 

I      I          I      I  #'/  CO/       / 


till          :  i  it  ii 

STREET  AND  PUBLIC       PRIVATE  ROAD      ROAD  CROSSING    ROAD  CROSSING    ROAD  CROSSING 
ROAD  CROSSINGS.  CROSSING.          AT  GRADE.       UNDERGRADE.        OVERHEAD. 

a...     .«  iw..    .    NOTE:  SPECIFY  STEAM  OR  ELECTRIC  WHERE  ELECTRIC 
RAILWAY  TRACKS.  TRACKS  CROSS  OR  JOIN  STEAM  TRACKS. 


RED.  RED.  COLOR  OTHER  THAN  RED  8R 


BLACK  WITH  INITIALS  OF  RMD 

RAILWAY  TRACK  OR      OLD  TRACK  TO  BE        PROPOSED         PROPOSED  (FUTURE)        FOREIGN 
OLD  TRACK  TO  REMAIN.       TAKEN  UP.  TRACKS  TRACKS.  TRACKS. 


*£* 

« 


TUNNEL.  TRACK  INSTRUMENT.      TORPEDO  MACHINE.      IMPEDANCE  BOND. 

<5^>  A 

ftR 


MILE  POST.         MAIL  CRANE.      WATER  TANK.      WATER  COLUMN.      TRACK  PAN. 

~  STOP. 

"~  CLEAR. 


NON-AUTOMATIC.  SLOTTED.       SEMI-AUTOMATIC.   AUTOMATIC. 

MECHANICAL.     .    POWER. 


INSULATED  TURNOUT  AND 

POWER  SWITCH  MACHINE.     SWITCH  ROD  SWITCH  STAND.       ELECTRIC  SWITCH  LOCK. 


± 


PLATE  III. 


APPENDIX 


333 


RELAY  Box 


D 


JUNCTION  Box 


CAPACITY- 


TERMINAL  Box    LIGHTNING  ARRESTER 
Box 

RELAY  BOX  CAPACITY. 


TAKE  OR  LEAWE        BATTERY 

SWN6  INOKATOR          CHUTE 


BATTERY  CWTE 


niw  ...., 

B°X  AN° 


BATTERY  CHUTE,  RELAY 
Box  AND  POST  COMBINED 


NOTE :  TYPE  OF  INDICATOR 

TO  B£  COVERED  BY 
)  GENERAL  NOTE 


SWITCH   Box  LOCATION 


SWITCH  INDICATOR 


SWITCH  INDICATOR 
AND  SWITCH  Box 


CD 


CABLE  POST    WITH  ONE 
ONLY          INDICATOR 

BATTERY  SHELTERS 
p—  -a 
[  5  j    ABOVE  SURFACE 


WITH  Two     WITH  RELAY    WITH  RELAY    WITH  RELAY 
INDICATORS         Box          Box  AND  ONE     Box  AND  Two 
INDICATOR       INDICATORS 


HALF  ABOVE  SURFACE 


BELOW  SURFACE 


(FIGURES    INDICATE  CAPACITY) 


AUDIBLE 


VISIBLE 


HIGHWAY  CROSSING  SIGNALS 


CR 


TRACK  BATTERY 


PLATE  IV. 


334 


RAILWAY  SIGNALING 


SWITCHES  AND  DERAILS 

SINGLE  SWITCH 


SET  FOR  TURN-OUT 


SET  FOR  STRAIGHT  TRACK 


SET  FOR  LEFT  TURN-OUT 


SET  FOR  STRAIGHT  TRACK         SET  FOR  RIGHT  TURN-OUT 


LEFT  HAND  DERAILS  RIGHT  HAND 

(NON-OERWUNG)  (DERAILING)  (NON-DERAILING) 


LIFTING  BLOCK  W 

NOTE    NON-INTERLOCKED  SWITCHES  AND  DERAILS  TO  BE  SHOWN  SAME  AS  ABOVE  EXCEPT  SHADING  IN  TRIANGLES  OMITTED 
WHERE  HAND-THROWN  SWITCHES  ARE  PIPE-CONNECTED  TO  OTHERS,  AT  LEAST  ONE  SWITCH  OR  DERAIL 
(THE  ONE  FARTHEST  FROM  POINT  OF  OPERATION)  SHOULD  HAVE  THE  LETTER  "P"  PLACED  BESIDE  IT. 


1— ••?- 1—  «•=_ — L-wrjr-Tl — i-^-r-JT-T 

Baa  LOCKED  SWITCH   PLUNGER  LOCKED    FACING  POINT  LOCK    SWITCH  AND  LOCK 
SWITCH  MOVEMENT 


OIL  ENCLOSED  PIPELINE 


OIL  ENCLOSED  WIRE  LINE 


PIPE  ADJUSTING  SCREW 


WIRE  ADJUSTING  SCREW 


CRANKS 


COMPENSATOR 


ARROW  INDICATES  DIRECTION 
OF  MOVEMENT  OF  PIPE  LINE- 
NORMAL  TO  REVERSE 


3-Ww 


3-WAY 


TRACK 


I5^p3     INTERLOCKING  OR  BLOCK  STATION      f\»7| 

Ir   T  N     SHOWM6  RBXnVE  POSTDON  OF  STATON,  OPEWTOR  AND  TRACK       V"~~"^ 

OPERATOR  FACING  TRACK  OPERATOR  WITH  BACK  TO  TRACK 

NOTE:  UNLESS  OTHERWISE  SPECIFIED  ON  PLAN  IT  WILL  BE  ASSUMED  THAT  WHERE  AN  INTERLOCKED 

SI6NAL  IS  SHOWN  CLEAR   OR  A  DERAIL  SHOWN   IN    NON-DERAILING   POSITION   THE  CON- 
TROLLING LEVER   IS  REVERSED,  AND  THAT  ALL  OTHER  LEVERS  ARE   NORMAL. 


PLATE  V, 


APPENDIX 


335 


INTERLOCKED  SWITCHES,  DERAILS,  ETC. 


M.P.F. 


SINGLE  LINE  PLAN 
EXPLANATION 


I  -SIMM  TURN -DOT 
2 -SIMPLE  CROSS-OVER 
3  -  DERAIL -SiN6U  POINT 
4-SiN6Lt  SLIP  SWITCH 


5 -DOUBLE  SLIP  SWITCH 
6  -  MOVABLE  POINT  CROssme  FROS    (M.P.F.) 
7-5iN6L£  SLIP  SWITCH  WITH  M.P.F. 
8 -DOUBLE  SLIP  SWITCH  WITH  M.P.F. 
9  -  RIGID  CROSSING  FROG 


ROCKING  SHAFT  LEAD-OUT 


PIPE    LINE 

WIRE    UNE 

P  WHEEL 

| 

i 

I 

1     L 

4      W 

i    1 

•4  '           ' 

1234       67  89 

CRANK  LEAD-OUT 


Z-  WAY  CRANK 


1- WAY  CRANK*! 


y2-WAY  CRANKS 


I  I    I3|4|    |6|7| 
VERTICAL  CRANKS 


DEFLECTING  BAR  LEAD-OUT 


HORIZONTAL  DEFLECTING  BARS 


fi 


123  678 

VERTICAL    DEFLECTING    BARS 


PLATE  VI. 


336  RAILWAY  SIGNALING 


RELAYS,  INDICATORS  AND  LOCKS* 

ELEMENTS  OF  SYMBOLS    T"T 

TO  BE  COMBINED  AS         JLJ-  D .  C .  ELECTRO  MAGNET. 

NECESSARY*  I  I 

KL        A. C. ELECTRO  MAGNET. 

I.!        COIL  ENERGIZED  OR  DE-ENERGIZED. 

tmmr  "I"~T 

i..i.j       i._i|       NEUTRAL  FRONT  CONTACT  -  CLOSED  OR  OPEN. 

»•-»  T  "  * 

i..i         ..  J.        NEUTRAL  BACK  CONTACT  -  CLOSED  OR  OPEN  . 
POLARIZED  ARMATURE  -  WITH  CONTACTS. 


X 


3  -POSITION  ARMATURE -WITH  CONTACTS. 


.1 

.-i!       HIGH  CURRENT  CONTACT. 


T""7 

l-.il       MAGNETIC  BLOW-OUT  CONTACT. 

]Ql        BELL  ATTACHMENT. 

IZH        DOUBLE  WINDING  -SPECIFY  IP  DIFFERENTIAL. 

^""T 

J-*        SLOW  ACTING. 

r       A 

J.        i.  .1        Disc  TVPE  INDICATOR  .  O  «  Disc  INVISIBLE.  •  -  Disc  VISIBLE. 


i.J.    L.i    i..L    J..1        SEMAPHORE  TYPE  INDICATOR. 


£&  OR  i^i*0*  i&i      WIRE  WOUND  ROTOR. 

-£i 

STATIONARY  WINDING.  I^-HIGH  VOLTAGE  WINDINB. 


£2 

QPO 


k_.i    1..1    L.I    1..L        ELECTRIC  LOCK- SHOW  SEGMENTS  FOR  LEVER  IN  NORMAL 
POSITION  . 

(SEE  NEXT  PAGE  FOR  EXAMPLES  OF  COMBINATIONS.) 


PLATE  VII. 


APPENDIX 


337 


RELAYS  ,  INDICATORS  AND  LOCKS. 

EXAMPLES   OF  COMBINATIONS. 

D.C.  RELAY-  NEUTRAL- ENERGIZED  - 

ONE  INDEPENDENT  FRONT  CONTACT  CLOSED - 
ONE  INDEPENDENT  BACK  CONTACT  OPEN. 

D.C.RELAY-  POLARIZED -ENERGIZED  — 

Two  COMBINATION  FRONT  AND  BACK  NEUTRAL  CONTACTS  < 
Two  POLARIZED  CONTACTS  CLOSED  — 
Two  POLARIZED  CONTACTS  OPEN. 


0.  C.  INDICATOR  -  SEMAPHORE  TYPE-  ENERGIZED  - 
THREE  FRONT  CONTACTS  CLOSED  - 
BELL  ATTACHMENT  . 


D.C.  INDICATOR-  SEMAPHORE  TYPE  -  ARM  HORIZONTAL  - 

ENERGIZED  -  WITHOUT  CONTACTS  . 
NOTE :  INDICATORS  (OR  REPEATERS)  WITHOUT  CONTACTS  SHOULD  BE  SHOWN 

WITH  ARMATURES  TO  INDICATE  WHETHER. ENER&ZED  OR  DC-ENER- 
GIZED. 

A. C.  RELAY-  ONE  ENERGIZING  CIRCUIT  TYPE  (SINGLE  PHASE) 
ENERGIZED -ONE  FRONT  CONTACT. 


-o- 


A.C. RELAY- Two  ENERGIZING  CIRCUIT  TYPE- ENERGIZED 
WIRE  WOUND  ROTOR - 
Two  NEUTRAL  FRONT  CONTACTS  . 


A.C.  RELAY-Two  ENERGIZING  CIRCUIT  TYPE -ENERGIZED — 
WIRE  WOUND  ROTOR  - 
Two  POLARIZED  CONTACTS. 

A.C  RELAY-Two  ENERGIZING  CIRCUIT  TYPE- ENERGIZED 
STATIONARY  WINDINGS  — 
ONE  NEUTRAL  FRONT  CONTACT— 
Two  3- POSITION  CONTACTS. 

D.C*  INTERLOCKED  RELAY. 


D.C. ELECTRIC  BELL. 


KSI6NATE  RESISTANCE  IN  OHMS  OF  ALL  D.C. RELAYS,  INDICATORS  AND  LOCKS. 


PLATE  VIII. 


22 


338 


RAILWAY  SIGNALING 


CIRCUIT  CONTROLLERS  OPERATED  BY  LEVERS. 

USE  EITHER  LETTER  SYSTEM  OR  GRAPHIC  SYSTEM. 


LEVERS  WITH  EXTREME  END  POSITION  AS  NORMAL. 

N-  FULL  NORMAL  POSITION  OF  LEVER 
B -NORMAL  INDICATION  POSITION. 
C- CENTRAL  POSITION. 
D- REVERSE  INDICATION  POSITION. 
R-FULL  REVERSE  POSITION. 


LEVERS  WITH  MIDDLE  POSITION  AS  NORMAL. 

N- NORMAL  POSITION. 
L-FULL  REVERSE  POSITION  TO  THE  LEFT. 
B -INDICATION  POSITION  TO  THE  LEFT. 
D-INDICATION  POSITION  TO  THE  RIGHT. 
R-FULL  REVERSE  POSITION  TO  THE  RIGHT. 


NOTE:  HEAVY  HORIZONTAL  LINES  INDICATE  PORTION  OF  CYCLE  OF  LEVER  THROUGH  WHICH  CIRCUIT  is  CLOSED. 


PLATE  IX. 


APPENDIX 


339 


CIRCUIT  CONTROLLERS  OPERATED  BY  SIGNALS. 

UPPER  QUADRANT.  LOWER  QUADRANT. 


3 -POSITION 
SIGNALS. 


CLOSED  AT  0  ONLY. 


IV 

T>—  tsj 

frx   4       CLOSED  AT  45°OMLY.         4>* 


J2T 


'' 


60^-70°  OR 
75   SIGNALS. 


CLOSED  AT  90  ONLY. 


CLOSED  O°TO  45° 


CLOSED  45°TO  90° 


CLOSED  AT  0  ONLY. 

CLOSED  IN  CLEAR 
POSITION  ONLY. 


1^^— 


>          r 

v 


CLOSED. 
OPEN. 


CIRCUIT  CONTROLLER  OPERATED  BY  LOCKINS 
SWITCH   CIRCUIT   CONTROLLER.         MECHANISM  OF  A  SWITCH  MOVEMENT. 


+->-+ 


CLOSED. 
OPEN. 


BRIDGE  CIRCUIT   CONTROLLER. 


POLE  CHANGING  CIRCUIT  CONTROLLER. 


SPRING  HAND  KEY  OR  PUSH  BUTTON. 


CIRCUIT  SWITCH 


PLATE  X. 


340 


RAILWAY  SIGNALING 


S-r- 

•1 


MANUAL  TIME  RELEASE. 
(  ELECTRIC) 

- 


AUTOMATIC  TIME  RELEASE. 
(ELECTRIC) 


ft 

FLOOR  PUSH, 


MANUAL  TIME  RELEASE  , 
(  ELECTRO  -MECHAH'L.) 


EMERGENCY  RELEASE 
(ELECTRIC) 


OPEN.  CLOSED. 

LATCH  CONTACT.      TRACK  INSTRUMENT  CONTACT. 


KNIFE  SWITCHES. 


Qr  <t>  d>   d>  <D  0  <D 

RHEOSTAT.     SINGLE  POLE.  DOUBLE  POLE.    SINGLE  POLE.  DOUBLE  POLE. 
SINGLE  THROW.  DOUBLE  THROW. 


QUICK  ACTING  CIRCUIT  CONTROLLERS  MAY  BE  DISTINGUISHED  BY  THE  LETTER  "9 


FIXED  RESISTANCE  .        VARIABLE  RESISTANCE  . 


FUSE. 


IMPEDANCE   WITHOUT 
IRON  CORE. 


000000 


IMPEDANCE  WITH 
IRON  CORE 


CONDENSER. 


PLATE  XI. 


APPENDIX 


341 


BATTERY. 


RECTIFIER 

UJ 


A.C.TERMINALS 


J  D.C.TERMINALS 
CELLS  IN  MULTIPLE  CELLS  IN  SERIES 

SPEC.FY  TYPE  AND  NUMBER  OF  CELLS  TRANSFORMERS 

D  =  DRY    BATTERY 
G  =  GRAVITY  »» 
P  =  POTASH   >» 
5  =  STORAGE  » 

EXAMPLES:  I6P,  IOS,  ETC. 


I-  SECONDARY      2-  OR  MORE  SECONDARIES 


(M) 

D.G.MOTOR 


roooooWj         (W\  (W\ 

I- SECOND   - 

JiCL05 

I  VV V  0 


FOR  GROUNDING  CASE      FOR  GROUNDING  SHIELD 

(|) 

D.C.  GENERATOR  A.C.  MOTOR 


|) 

A.C.  GENERATOR 


AMMETER 


INCANDESCENT  LAMP 


O.C.-*D.C.  MOTOR-  GENERATOR     A.C.-D.C.  MOTOR-  GENERATOR 


-<w>— 


VOLTMETER  WATTMETER        TELEPHONE 


SINGLE  DOUBLE 

LIGHTNING  ARRESTER  TERMINALS 


WIRES  GROSS 


WIRES  JOIN 


JL 


6ROUND 


"  COMMON  "  WIRE 


OTHER  THAN  "  COMMON" WIRE 


TRACK  CIRCUIT  WIRE 


DIRECTION  OF  CURRENT 


PLATE  XII. 


342 


RAILWAY  SIGNALING 


EXPLANATORY  DIAGRAMS 


SWflOCK 


POLE  LINE 


1 


TRUE  MERIDIAN     STAFF  INSTRUMENT  STAFF  CRANE      YARD  LIMITS 

SKNAL  CONTROL  LjMlTS     ^ 


EXPLANATORY   NJfCS: 


TMINM  ncne«s  •W%^nr<tN>WM  »T 'rrw^  sxKin.w-l,  4,oe. 

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WCSTVMTO  TVAIN  ON  'F"C*  NOUS  AT  41  ON.  MSNA8  NO. 2  MO  AT  'STOP1  SWK«L  H9.6. 


AIR  PIPE  AND  FITTINGS 


""«  X 

EXPANSION  JOINT         PIPE 
ANCHOR 


REDUCERS  AND  BUSHINGS 
FONT  TO  SMALLER  PIPE 


COMBINATION  COCK 
AND  UNION 


MANIFOLD*  CONDENSER 


SPLICING  CHAMBER     RAIL  LOCKS 


RUNS  OF  CONNECTIONS 

PIPE-WIRE  (MECH.) 


EROUND         DWARF 

BRIDGE  LOCK          MECHANICAL          LEVERS        MACHWE 
BRIDGE  COUPLER 

SPECIAL  i  CONTACTS 


0=  CONTACT  ON  DRAW  WEDGES 
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PIPE-WIRE  AND  DUCT 
PIPE -WIRE  AND  AIR 
DUCT  AND  AIR 
PIPE-WIRE,  DUCT  AND  AIR 


rwN  REUV  \ 

CONTACTS  CLOSED  TO  ONE  EXTREME    DROP  ANNUNCIATOR 
NEUTRAL 


PLATE  XIII. 


APPENDIX  C 
A  DEFINITION  OF  TERMS  USED  IN  RAILWAY   SIGNALING1 

Absolute  Block  Signaling. — The  method  of  signaling  which  requires  that 

no  train  be  admitted  to  a  block  while  another  train  occupies  it. 

Acute  Angle  Crank. — A  two-arm  crank,  the  arms  of  which  subtend  an 
angle  of  less  than  90  degrees. 

Adjustable  Link. — A  link,  the  length  of  which  can  be  varied. 

Adjusting  Screw. — A  screw  for  regulating  the  relative  positions  of  parts 
of  apparatus,  or  for  changing  the  tension  in  a  wire  line. 

Advance. — The  condition  of  being  in  an  advance  position,  as  a  signal  in 
relation  to  a  train  approaching  it. 

Advance  Signal. — A  signal  having  the  same  function  as,  but  placed  some 
distance  in  advance  of,  the  home  signal  at  a  block  or  interlocking  station  to 
provide  a  short  block  section  in  which  a  train  may  be  held  so  as  not  to 
interfere  with  the  movements  of  trains  in  the  adjacent  block  sections. 

Advance  Block  Signal. — A  fixed  signal  used  in  connection  with  a  home 
block  signal  to  sub-divide  the  block  ahead. 

Air  Gap. — Any  space  occupied  by  air  in  a  magnetic  or  electric  circuit. 

Alarm. — Any  sound  or  information  intended  to  give  notice  of  approaching 
danger;  a  warning  sound  to  arouse  attention. 

All-air  Interlocking. — An  interlocking  plant jtheunits  of  which  are  oper- 
ated by  compressed  air  only. 

Annunciator. — A  device  to  announce  by  an  audible  or  visual  indication, 
usually  in  an  interlocking  or  block  station,  the  approach  of  a  train. 

Answer-back  Signal. — A  signal  arranged  to  give  a  visual  or  audible 
indication  of  the  completion  of  a  movement. 

Anti-friction  Pipe  Carrier. — A  pipe  carrier  in  which  the  movable  parts 
carry  the  pipe  without  friction. 

Approach  Indicator. — An  indicator  which  announces  the  approach  of  a 
train. 

Approach  Locking. — Electric  locking  effected  by  the  approach,  or  released 
by  the  passing,  of  a  train,  through  the  medium  of  a  track  circuit  or  track 
instrument. 

Arm. — The  principal  movable  part  of  a  semaphore,  consisting  of  a  blade 
of  wood  or  metal  fastened  to  a  casting  which  turns  on  a  supporting  pivot. 

Arm  Casting. — The  part  of  a  semaphore  arm  to  which  the  blade  is  fas- 
tened, and  which  contains  the  bearing  and  the  spectacles  for  holding  the 
glasses  through  which  the  night  color  indications  are  given. 

Arm  Sweep. — The  portion  of  a  circle  included  between  any  two  positions 
of  a  semaphore  arm. 

Aspect. — The  position  of  a  signal  arm  usually  considered  in  its  relation 
to  the  signal  mast  or  a  perpendicular  thereto.  The  appearance  of  a  signal 

1  Proceedings,  Railway  Signal  Association,  1914. 

343 


344  RAILWAY  SIGNALING 

conveying  an  indication  as  viewed  from  the  direction  of  an  approaching 

train. 

^ Audible  Signal. — A  signal, giving  .an  audible  indication. 

Automatic. — A  term  applied  to  signals  which  assume  their  various  aspects 

through  the  exercise  of  inherent  power,  as  distinguished  from  those  in  which 

the  changes  are  made  manually. 
^  Automatic  Block  Signal.— A  block  signal  having  an  inherent  power  of 

motion  which  is  controlled  by  the  passage  of  a  train  into,  through,  and  out  of, 

the  block  section  which  the  signal  governs,  and  by  the  integrity  of  the  track 

within  that  block. 
I        -  .        Automatic  Block  Signal  System. — A  series  of  consecutive  blocks,  the  use 

of  which  by  trains  is  controlled  by  automatic  block  signals. 
y,        ^ Automatic  Block  System. — A  series  of  consecutive  blocks  controlled  by 

block  signals  operated  by  electric,  pneumatic,  or  other  agency,  actuated  by 

a  train  or  by  certain  conditions  affecting  the  use  of  a  block. 

Automatic  Stop. — An  apparatus  which,  under  certain  conditions,  operates 

in  conjunction  with  an  outside  agency  to  stop  a  train  automatically  by 

shutting  off  the  motive  power,  or  applying  the  brakes,  or  both. 

B 

Back  Light. — A  light  showing  through  a  small  glass-covered  opening 
in  the  back  of  a  signal  lamp. 

Back  Lock. — See  Indication  Lock. 

Back  Locking. — That  part  of  the  mechanical  locking  in  a  "Standard" 
interlocking  machine,  which  acts  back  of  the  tappets. 

Back  Spectacle. — A  small  casting  containing  a  roundel  at  one  end  and 
fastened  at  the  other  to  the  semaphore  shaft  of  a  signal  in  such  manner  as  to 
change  the  visible  color  of  the  back  light  when  the  signal  is  moved. 

Back  Tail  Lever. — The  tail  lever  of  a  mechanical  interlocking  machine 
which  projects  towards  the  back  of  the  machine. 

Back  Wire. — A  wire  connected  to  the  back  tail  lever  of  a  mechanical 
interlocking  machine  and  to  a  signal  so  that  it  will  insure  that  the  signal 
will  assume  its  normal  position  when  the  lever  is  put  normal. 

Balance  Lever. — A  lever  which  carries  a  signal  counterweight. 

Banjo  Signal. — A  term  commonly  applied  to  the  enclosed  disk  signal 
because  in  general  appearance  it  resembles  a  banjo. 

Banner  Signal. — A  common  name  for  the  clock  work  signal. 

Battery  Chute. — A  small  receptacle  for  batteries,  commonly  made  of  cast 
iron  and  sometimes  of  reinforced  concrete  or  fiber,  and  usually  cylindrical 
in  shape,  designed  to  hold  two  or  more  battery  cells. 

Battery  Elevator. — An  arrangement  of  shelves  in  a  supporting  frame  by 
means  of  which  batteries  may  be  lowered  into,  held  in  position  in,  and  raised 
out  of,  battery  chutes. 

Battery  Vault. — A  term  commonly  used  for  battery  well. 

Battery  Well. — A  container  for  batteries,  usually  made  of  reinforced 
concrete. 

Bell  Code. — A  code  in  which  the  strokes  of  a  bell  have  a  predetermined 
significance. 

Bell  Crank. — A  common  name  for  a  crank. 


APPENDIX  345 

Blade. — The  extended  part  of  a  semaphore  arm,  which  fiives  the  day  <^ 

indication. 

Blade  Grip. — The  part  of  a  semaphore  arm  to  which  the  blade  is  secured. 

Block. — A  section  of  track  of  defined  limits,  the  use  of  which  by  trains  is 
controlled  by  block  signals. 

Block  End,— The  end  of  a  block. 

Block  Indicator. — -An  r\ n re ro-magnetic  device  controlled  by  the  track 
circuit  of  a  track  section,  or  by  track  instruments,  to  indicate,  within  a 
signal  tower,  whether  or  not  that  track  circuit  is  occupied  by  a  train. 

Block  Instrument. — The  instrument  used  in  controlled  manual  block 
signaling  to  compel  the  cooperation  of  the  operators  at  both  ends  of  a  block 
in  allowing  a  train  to  enter  from  either  end. 

Block  Length. — The  length  of  a  block. 

Block  Office. — An  office  from  which  the  use  of  a  block  section  is  controlled. 

Block  Section. — A  section  of  track  of  denned  length,  the  use  of  which  by 
trains  is  regulated  by  a  fixed  signal,  at  the  entering  end  on  double  track,  and 
at  each  end  on  single  track. 

Block  Sheet. — The  sheet  on  which  movements  of  trains  are  recorded  at  a 
block  station. 

Block  Signal. — A  fixed  siflnal  at  tfr«  ^TltrTTVflM  to  ft  MW-k  «***•'""  t  "«*d  *» 
give  indications  regulating  the  movement  of  trains  into  that  block. 

Block  Signaling. — The  method  of  regulating  the  movements  of  railway 
trains,  so  as  to  maintain  an  interval  of  space  between  them. 

Block  Station. — A  place  from  which  block  signals  are  operated. 

Block  System. — A  series  of  consecutive  blocks. 

Bolt  Lock. — A  lock  so  arranged  that  if  a  switch  is  not  in  the  proper  position 
for  a  train  movement  the  signal  governing  that  movement  cannot  be  cleared, 
and  will  prevent  a  movement  of  the  switch  while  the  signal  is  in  the  clear 
position. 

Bond. — A  common  name  for  a  rail  bond. 

Bonding  Tube. — A  tapered  metal  tube  used  for  fastening  a  bond  wire  to 
a  rail. 

Bond  Wire. — A  common  name  for  a  part  of  a  rail  bond. 

Bonding  Plug. — A  piece  of  metal  resembling  a  rivet  in  shape  and  used  to 
fasten  the  wire  of  a  rail  bond  to  a  rail. 

Bootleg. — A  short  piece  of  the  wooden  trunking,  conduit,  or  conduit 
encased  in  concrete,  used  at  the  point  where  a  track  circuit  connection  is 
made  with  the  rail  to  enclose  a  part  of  the  wire  which  extends  from  the  rail 
to  a  battery  or  relay  box. 

Box  Crank. — Two  or  more  cranks  assembled  in  a  common  frame,  each 
crank  having  an  independent  bearing. 

Boxing. — A  wooden  covering  for  pipe  or  wire  lines. 

Box  Wheel. — Two  or  more  chain  wheels  assembled  in  a  common  frame, 
each  wheel  having  an  independent  bearing.  A  group  of  chain  wheels 
mounted  in  one  frame. 

Bracket  Mast. — A  signal  mast  above  and  supported  on  the  cross  piece  or 
deck  of  a  bracket  post. 

Bracket  Post. — An  arrangement  for  supporting  two  or  more  signals  side  by 
side  on  a  single  foundation. 


346  RAILWAY  SIGNALING 

Bracket  Signal. — A  signal  supported  on  a  bracket  mast. 

Bridge  Circuit  Controller. — A  device  for  connecting  and  disconnecting 
circuits  at  the  ends  of  a  movable  bridge  span. 

Bridge  Coupler. — A  device  for  engaging  and  disengaging  the  interlocking 
connections  crossing  a  movable  bridge  span. 

Bridge  Lock. — A  device  for  locking  a  movable  span  of  a  drawbridge  in  its 
closed  position,  so  interlocked  with  the  signals  governing  the  approach  to 
the  bridge  that  they  cannot  be  cleared  unless  the  bridge  is  in  the  closed 
position  and  locked. 

Bridge  Mast. — The  upright  mast  on  a  signal  bridge. 

Bus  Bar. — A  common  conductor  on  a  switchboard  or  other  terminal  from 
which  taps  may  be  made  for  taking  off  current  for  any  purpose. 

Butt  End. — A  term  applied  to  a  jaw  or  bar  the  end  of  which  is  cut  off 
without  tang  or  thread. 

C 

Cab  Signal. — An  arrangement  for  producing  visual  or  audible  indications 
on  moving  engines  or  cars  or  in  the  cab  of  a  locomotive  to  give  information 
concerning  the  condition  of  the  track  in  advance  or  of  the  fixed  signals  along 
the  track. 

CalJing-on  Arm. — A  semaphore  arm  used  to  permit  a  train  to  move  past 
a  home  signal  when  the  principal  arm  of  the  signal  has  to  be  left  at  "stop." 

Cantilever  Bracket  Post. — A  type  of  bracket  post  so  constructed  that  a 
signal  mast  thereon  will  be  located  in  proper  relation  to  the  track  governed. 

Capping. — The  covering  for  trunking. 

Caution. — A  term  used  for  the  caution  indication.     See  caution  indication. 

Caution  Card. — A  form  of  written  order  issued  to  a  train  to  permit  it  to 
enter  a  block  which  is  not  clear. 

Caution  Signal. — A  signal  giving  a  caution  indication  denoting  that  a 
train  may  proceed  under  some  restrictions  as  to  the  speed  of  running. 

Chain  Wheel. — A  wheel  used  in  transmitting  the  motion  of  one  part  of 
a  wire  line  to  another  part  which  extends  in  a  different  direction. 

Chain  Wheel  Stand. — A  casting  or  frame  carrying  one  or  more  chain 
wheels. 

Channel  Pin. — A  device  in  the  shape  of  a  truncated  cone,  in  which  is  cut  a 
longitudinal  slot,  and  which  is  used  to  fasten  a  wire  to  a  rail  by  wedging  the 
wire  in  a  hole  in  the  rail. 

Check  Locking. — A  method  of  interlocking,  electrically,  the  levers  in  two 
adjacent  interlocking  plants  to  permit  train  movements  between  them  to  be 
made  safely  against  the  current  of  traffic  and  as  the  result  of  cooperation  in 
each  movement  by  the  operators  at  the  interlocking  stations  concerned. 

Check  Lock  Lever. — In  an  interlocking  machine,  a  separate  lever  which  is 
used  for  check  locking. 

Choke  Coil. — A  reactance  used  in  connection  with  lightning  arresters  and 
placed  in  series  with  the  line  to  be  protected. 

Choke  Coil  Lightning  Arresters. — A  lightning  arrester  working  on  the 
choke  coil  principle. 

Clear  (verb). — To  cause  a  signal  to  assume  the  aspect  which  indicates 
that  a  train  may  proceed. 


APPENDIX  347 

Clearance  Card. — In  block  signaling,  a  written  order  issued  by  a  signal- 
man to  authorize  a  train  to  enter  a  block  when  the  signal  cannot  be  cleared. 

Clearance  Point. — The  point  within  the  angle  included  between  converg- 
ing tracks,  at  which  the  clearance  lines  of  those  tracks  intersect. 

Clear  Signal. — A  term  used  to  indicate  the  aspect  of  a  signal  which  indi- 
cates proceed. 

Clock woik  Signal. — A  disk  signal  revolving  on  a  vertical  spindle  and 
operated  by  clockwork. 

Common  Wire. — A  wire  which  is  used  to  form  a  part  of  the  paths  of 
current  in  two  or  more  electric  circuits.  Usually  applied  to  the  common 
return  wire. 

Compensator. — A  device  for  taking  up  the  effects  of  temperature  so  as  to 
maintain  a  constant  length  in  a  line  of  pipe  or  wire. 

Compound  Relay. — A  relay  having  double-wound  coils,  or  separate 
windings,  insulated  from  each  other. 

Concrete  Bootleg. — A  bootleg  made  from  concrete  and  conduit  and  used 
in  place  of  wooden  trunking,  for  enclosing  the  signal  wire  of  a  track  circuit, 
which  leads  down  to  the  horizontal  wire  leading  to  the  battery  or  relay  box. 

Conduit. — A  tube  of  wood,  clay,  iron  or  fiber,  enclosing  electric  wires, 
usually  underground. 

Contact  Rail. — In  automatic  train-stopping  or  cab-signaling  systems,  a 
bar  of  metal  fixed  on  the  ties  parallel  to  the  rails  of  the  track  in  such  a  way  as 
to  be  rubbed  by  an  electrical  conductor  carried  by  the  engine  or  train. 

Control  Circuit. — In  interlocking,  a  circuit  used  to  control  an  operated     .- 
unit  or  its  immediate  controlling  apparatus;  and  in  block  signaling,  a  circuit 
used  to  control  a  signal  at  some  distance  from  another  signal. 

Controlled  Manual  Block  System. — A  block  system  in  which  the  signals     *  -> 
are  operated  manually  by  mechanisms  so  constructed  that  the  displaying 
of  a  clear  signal  is  dependent  upon  the  cooperation  of  the  signalmen  at  both 
ends  of  the  block,  or  upon  the  absence  of  a  train,  or,  in  some  cases,  certain 
other  obstructions,  in  the  block,  or  both. 

Control  Wire. — A  wire  which  carries  current  from  its  source  to  an  operated 
unit  or  its  immediate  controlling  apparatus. 

Convertible  Lamp. — A  signal  lamp  equipped  for  the  use  of  either  oil 
burners  or  bulbs. 

Copper-clad  Wire. — An  electrical  conductor  made  with  a  steel  center,  sur- 
rounded by  copper. 

Counterweight. — In  a  semaphore,  a  weight  so  arranged  that,  in  case  of 
breakage  of  the  wire,  or  the  pipe  controlling  the  signal,  the  weight  will  pull 
the  signal  to  the  stop  position. 

Counterweight  Lever. — A  lever  on  a  signal  or  interlocking  machine  for 
the  support  of  a  counterweight. 

Crank. —  A  lever,  the  arms  of  which  form  an  angle,  with  the  fulcrum  at 
the  vertex  of  the  angle,  which  is  used  to  transmit  the  motion  of  one  part 
of  a  line  of  pipe  to  another  part  which  extends  in  a  different  direction. 

Crank  Stand. — A  frame  in  which  one  or  more  cranks  are  supported. 

Cross. — The  accidental  electrical  contact  of  conducting  wires. 

Crossing  Bar. — A  detector  bar  operated  from  a  lever  in  an  interlocking 
machine  and  used  to  prevent  the  changing  of  a  route  over  a  railway  crossing 
while  that  crossing  is  occupied  by  a  train. 


348  RAILWAY  SIGNALING 

Crossing  Gate. — A  gate  which  is  lowered  on  either  or  both  sides  of  a  rail- 
way line  across  a  public  highway,  to  close  the  highway  against  traffic  while 
a  train  is  passing. 

Crossing  Protection. — Any  arrangement  of  signaling  or  interlocking  facili- 
ties designed  to  prevent  collisions  at  a  railway  crossing. 

Cross  Lock. — A  part  of  the  locking,  in  a  machine  of  the  Saxby  &  Farmer 
type,  which  is  moved  by  a  locking  dog  in  a  direction  at  right  angles  to  the 
movement  of  the  dog. 

Cross  Locking. — The  arrangement  of  the  cross  locks  in  an  interlocking 
machine  of  the  Saxby  &  Farmer  type. 

Crossover. — A  short  track  leading  from  one  to  the  other  of  two  parallel 
tracks. 

Cross  Protection. — The  arrangement  of  electrical  conductors  and  in- 
struments to  prevent  damage  to,  and  improper  operation  of,  electrical 
apparatus  from  the  effects  of  a  cross,  or  to  allow  only  such  operations  as  are 
necessary  to  obviate  the  possibility  of  danger. 

Crowfoot  Zinc. — A  form  of  zinc  plate  used  in  a  gravity  cell,  with  a  vertical 
stem  and  several  radiating  spokes  or  toes,  resembling  the  foot  of  a  bird. 

Current  of  Traffic. — The  normal  movement  of  trains  in  a  given  direction. 

Cut  Section. — A  track  circuit  section  which  requires,  at  a  point  within  its 
length,  the  relaying  of  the  effect  of  a  change  in  its  condition. 

Cycle. — In  an  alternating  current  a  complete  change  in  direction  from 
any  given  value  through  zero  to  an  equal  value  in  the  opposite  direction  and 
back. 

D 

Danger. — A  term  formerly  used  to  denote  the  stop  indication  of  a  signal 
(obsolete). 

Dash  Pot. — A  device,  comprising  a  cylinder  in  which  a  fluid  acts  as  a 
cushion  for  a  falling  weigfit  attached  to  a  piston  within  the  cylinder. 

Deflecting  Bar. — A  device  which,  by  means  of  a  curved  bar  sliding  end- 
wise between  rollers,  transmits  the  motion  of  one  part  of  a  line  of  pipe  to 
another  part  which  extends  in  a  different  direction. 
AA  fierfli^  ^nou^f—-/^r\y  HPVIP.P  in  a  fjftfifj  Inp.a.tion  for  throwing  train  wheels 

off  the  track  to  prevent  them  from  running  into  a  dangerous  situation. 
/<£        _.      Derailing  Switch. — A  switch  designed  to  turn  train  wheels  off  the  track 
to  prevent  them  from  running  into  a  dangerous  situation. 

Detector  Bar. — A  device  for  preventing  the  movement  of  a  switch  under  a 

£  train,  by  means  of  a  strip  of  metal  mounted  alongside  the  track  rail  and 

connected  with  a  lever  or  an  operated  unit  in  such  a  way  that  the  lever  or 

unit  is  prevented  from  being  moved  or  unlocked  as  long  as  the  presence  of 

train  wheels  prevents  the  bar  from  being  raised. 

Detector  Bar  Driving  Piece. — A  device  bolted  or  riveted  to  a  detector  bar, 
to  which  the  driving  rod  is  attached. 

Detector  Bar  Link. — A  short  link  supporting  a  detector  bar,  and  so  pivoted 
on  a  clip  fastened  to  a  track  rail  that  the  detector  bar  in  moving  longi- 
tudinally must  also  move  upward  and  above  the  top  of  the  rail. 

Detector  Bar  Stop. — A  lug  fastened  to  a  track  rail,  on  which  the  detector 
bar  rests  when  its  stroke  is  completed. 


APPENDIX  349 

Differential  Relay. — A  relay  having  two  sets  of  coils  so  arranged  that 
each  may  work  in  a  predetermined  relation  to  the  other. 

Disk  Signal. — A  signal  in  which  the  day  indications  are  given  by  the 


color,  or  by  the  absence  or  presence,  of  disks. 

Distant  Block  Signal. — A  fixed  signal  located  in  the  rear  of  one  or  more 
home,  or  home  and  advance  block  signals,  so  controlled  Toy  them  that  it 
gives  the  indication  "prepare  to  stop,"  when  any  controlling  signal  indicates 
stop,  and  may  give  the  proceed  indications  only  when  all  controlling  signals 
are  clear  (or,  in  some  cases,  also  when  they  give  the  caution  indication); 
and  used  to  convey  information  as  to  the  indications  of  such  signals  before 
the  trains  reach  the  home  block  signals. 

Distant  Indication. — An  indication  which  is  conveyed  by  the  aspect  of  a 
distant  signal. 

Distant  Signal. — A  fixed  signal  used  in  connection  with  a  home  signal  to 
regulate  the  approach  thereto. 

Distant  Switch  Signal. — A  signal  used  to  indicate  the  position  of  the 
points  of  a  switch. 

Dog  Chart. — A  diagrammatic  representation  of  the  mechanical  locking 


for  an  interlocking  machine;  used  as  a  working  plan  in  making  up  and  fitting 
the  locking. 

Doll. — A  term  used  sometimes  to  designate  a  short  signal  post,  as  the 
bracket  mast  of  a  bracket  signal. 

Double  Jaw. — A  special  form  of  jaw  for  making  an  intermediate  connec- 
tion to  a  pipe  line. 

Double -slip  Switch. — A  diagonal  crossing  of  two  tracks,  with  switch 
points  and  frogs  so  arranged  that  a  train  on  either  track,  in  either  direction, 
can  proceed  on  either  track  beyond  the  crossing. 

Double  Slot. — A  combination  of  two  slots  in  one  case  for  the  control  of 
two  signal  blades  on  one  mast. 

Drawbridge  Lock. — A  mechanical  device  to  lock  in  alignment  the  rails  on 
a  drawbridge. 

Drop -a way. — The  point  in  the  gradual  reduction  of  the  amount  of  current 
flowing  through  the  coils  of  an  electro-magnet  at  which  the  amount  or  value 
of  the  current  is  such  as  to  permit  the  armature  to  drop  away  from  the  cores 
of  the  magnet  coils. 

Dummy. — A  bracket  mast  on  a  bracket  signal  bearing  no  signal  arm  and 
designed  merely  to  aid  by  its  location  relative  to  the  other  bracket  mast  in 
showing  to  which  of  two  or  more  tracks  a  signal  applies. 

Dwarf  Interlocking  Machine. — An  interlocking  machine  of  small  propor- 
tions, commonly  used  in  the  open. 

Dwarf  Signal. — A  low  fixed  signal.  Similar  to  and  having  the  same 
functions  as  a  standard  home  signal. 

E 

Electric  Bolt  Lock. — An  electric  lock  which  insures  that  the  switch  and 
the  signal  governing  movements  over  it  are  in  their  proper  relative  positions 
before  either  can  be  moved. 

Electric  Bridge  Coupler. — A  device,  one  part  of  which  is  placed  on  a  draw- 
bridge, with  the  other  part  on  the  abutment,  and  which  is  operated,  directly 


350  RAILWAY  SIGNALING 

or  indirectly,  by  a  lever,  and  is  so  arranged  that  a  number  of  circuits  passing 
through  it  can  be  closed  only  when  the  bridge  is  closed  and  locked. 

Enclosed  Disk  Signal. — A  signal  in  which  a  colored  disk  is  displayed 
behind  a  glass  front  in  a  closed  case  to  form  the  stop  or  caution  aspect,  and 
withdrawn  from  sight  to  form  the  proceed  aspect  of  the  signal. 

Electric  Lock. — A  device  which  locks  the  lever  of  an  interlocking 
machine  to  prevent  its  movement,  until  it  is  released  by  an  electro- 
magnet. 

Electric  Interlocking.— Interlocking  in  which  the  operated  units  are 
operated  and  controlled  by  electricity. 

Electric  Motor  Signal  Mechanism. — A  signal  mechanism  operated  by  an 
electric  motor  which  is  controlled  by  electric  apparatus. 

Electric  Selector. — An  electro-mechanical  device  by  which  the  electric 
circuit  of  any  one  of  a  number  of  audible  or  visible  signals  or  other  devices 
may  be  controlled  from  a  distant  point  without  affecting  any  of  the  other 
apparatus  or  devices. 

Electric  Slot. — A  device  in  which  the  connection  between  a  signal  arm  and 
its  operating  mechanism  is  controlled  by  an  electro-magnet,  the  connection 
being  broken  when  the  magnet  is  deenergized,  and  established  when  the 
parts  are  in  proper  mechanical  relation  and  the  magnet  energized. 

Electric  Switch  Lock. — An  electric  lock  controlled  from  a  signal  cabin  and 
attached  to  the  operating  connection  of  an  outlying  switch  to  prevent  the 
switch  from  being  moved  without  the  knowledge  and  consent  of  the  signal- 
man in  the  cabin. 

^Electric-Xgam  Staff  System. — A  method  of  regulating  the  movements  of 
trains  in  which  the  possession  of  a  metal  staff  or  a  part  thereof  gives  per- 
mission to  a  train  to  enter  a  block,  the  staffs  being  kept  in  machines  at  the 
ends  of  the  block,  which  are  so  electrically  locked  between  adjacent  stations 
that  only  one  staff  and  the  sections  thereof  can  be  out  of  the  two  machines  at 
one  time. 

Electro-gas  Signal. — A  semaphore  signal  worked  by  compressed  carbonic 
acid  gas  which  is  controlled  by  electric  apparatus. 

Electrolyte. — The  exciting  fluid  surrounding  the  plates  or  elements  of  an 
electric  cell,  containing  in  solution  the  chemicals  which  act  on  the  elements 
to  produce  an  electro-chemical  current. 

Electro -magnet. — A  device  comprising  one  or  more  coils  of  insulated  wire 
wound  around  a  soft  iron  or  steel  core,  and  depending  for  its  magnetic  action 
upon  the  passage  of  an  electric  current  through  the  wire. 

Electro -mechanical  Slot. — A  device  consisting  of  an  electro-magnet  with 
levers  and  rods  enclosed  in  a  case  and  placed  on  the  signal  post  so  that  it 
controls  the  connection  between  the  signal  arm  and  its  operating  mech- 
anism, and  used  to  prevent  a  signal  from  being  cleared,  or  to  cause  the  signal 
to  move  to  the  stop  position  when  the  route  governed  by  the  signal  is 
obstructed. 

Electro -pneumatic  Interlocking. — Interlocking  in  which  the  units  are 
operated  by  compressed  air,  the  application  of  which  is  controlled  by 
electricity. 

Electro -pneumatic  Signals. — Signals  which  are  operated  by  compressed 
air,  the  application  of  which  is  controlled  by  electricity. 


APPENDIX  351 

Escapement  Crank. — A  crank,  used  in  a  "switch  and  lock"  movement,  by 
means  of  which  a  single  stroke  of  a  lever  performs  the  three  operations  of 
raising  the  detector  bar  and  unlocking  a  switch ;  moving  a  switch ;  and  lower- 
ing the  detector  bar  and  locking  the  switch. 


Facing  P»jnt  T.nr.k. — A  WV  fnr  a,^  interlocked  switch.  d«>^j]  nr  f™n 
comprising  a  plunger  which  engages  a  lock  rod  attached  to  the  switch  points 
to  lock  the  switch  in  its  normal  or  reverse  position. 

Facing  Point  Switch. — A  switch,  the  entering  end  of  which  is  toward  an 
approaching  tram. 

False  Clear  Signal. — A  signal  which  fails  to  indicate  when  the  condition  of 
the  block  governed  by  it  is  such  as  to  make  it  unsafe  to  proceed. 

Fixed  Blade  Signal. — A  signal  of  fixed  aspect,  serving  as  a  marker  of 
location,  having  no  moving  parts  and  permanently  indicating  caution  or 
stop. 

Fixed  Signal. — A  permanent  signal  of  fixed  location  with  reference  to  the 
track,  indicating  condition  affecting  the  movements  of  trains,  as  distin- 
guished from  signals  given  by  a  motion  of  the  hand  or  by  a  flag  or  lamp. 

Floor  Push. — An  electric  circuit  closer  fixed  in  the  floor  so  that  a  circuit 
may  be  made  by  pressure  on  a  plunger. 

Fouling  Bar. — A  detector  bar,  placed  at  or  near  a  fouling  point  to  prevent 
the  movement  of  a  unit  while  a  train  is  on  the  bar. 

Fouling  Point. — See  clearance  point. 

Foundation. — A  fixed  support,  usually  set  in  the  ground,  for  carriers, 
cranks,  compensators,  wheels,  signals  and  other  like  devices. 

F.P.L. — The  abbreviation  for  facing  point  lock. 

Frequency. — The  number  of  double  alternations  or  periods  made  by  an 
alternating  electric  current  relay,  so  made  that  it  will  act  effectively  only 
when  energized  by  an  alternating  current  of  given  frequency. 

Frequency  Relay. — An  alternating  current  relay,  so  made  that  it  will  act 
effectively  only  when  energized  by  an  alternating  current  of  the  given 
frequency. 

Front  Contact. — A  part  of  a  relay  against  which,  when  the  relay  magnets 
are  energized,  the  current-carrying  portion  of  the  armature  is  held  so  as  to 
form  a  continuous  path  for  current. 

Front  Rod. — A  rod  attached  to  the  extreme  point  of  a  switch  and  to  which, 
in  turn,  the  lock  rod  is  fastened. 

Front  Spectacle. — The  spectacle  of  the  semaphore  signal  which  holds  the 
blade.  See  blade  casting. 

Full  Normal. — The  condition  of  being  in,  and  latched  in,  the  normal  posi- 
tion, as  applied  to  the  lever  of  an  interlocking  machine ;  or  of  being  in,  and 
locked  in,  the  normal  position,  as  applied  to  an  operated  unit. 

Function. — The  activity  appropriate  to  the  performing  or  discharging  of  a 
duty  or  purpose.  See  Operated  Unit. 

Fusee. — An  auxiliary  signal  consisting  of  a  tube  of  chemical  compound 
which  will  burn  for  a  predetermined  length  of  time  with  a  colored  light, 
generally  red  or  yellow,  and  which  is  equipped  with  a  sharp  point  so  that  it 
can  be  thrown  to  stand  upright  in  the  track. 


352  RAILWAY  SIGNALING 

G 

Gravity  Cell. — A  two-fluid  primary  cell,  in  which  the  electrolytes  are  kept 
separate  by  the  difference  in  their  specific  gravity,  the  denser  liquid  resting 
at  the  bottom  of  the  jar  while  the  lighter  solution  stays  on  top. 

Ground  Machine. — An  interlocking  machine  so  constructed  and  arranged 
that  it  can  be  placed  on  the  surface  of  the  ground. 

Ground  Mast. — A  signal  mast  with  its  base  at  or  near  the  surface  of  the 
ground.  Usually  supported  on  a  foundation. 

H 

Half -reversed. — The  condition  of  being  midway  between  full  normal  and 
full  reverse  as  applied  to  the  lever  of  an  interlocking  machine  or  current 
breaker  of  a  lever  or  signal. 

Half -reverse  Lock. — An  electric  lock  applied  to  the  lever  of  an  interlocking 
machine  to  prevent  the  lever  from  going  to  its  full  normal  position  until 
certain  operations  have  been  performed,  such  as  the  passing  of  a  train  over 
a  track  circuit,  or  the  operations  of  a  hand  release. 

Hand  Release. — A  device,  used  in  connection  with  an  interlocking 
machine  to  insure  that  after  a  route  has  been  set  up  or  a  lever  movement 
made,  an  interval  of  time  must  elapse  before  the  route  can  be  changed 
or  the  lever  manipulated. 

Head  Block. — One  of  the  end  ties  on  which  the  points  of  a  switch  and  the 
switch  stand  rest. 

Head  Rod. — That  one  of  the  rods  which  connect  the  two  points  of  an 
interlocked  switch  which  is  used  for  throwing  the  switch. 

High  Signal. — A  full-sized  semaphore  mounted  on  a  mast,  bridge,  building 
or  other  structure  above  the  level  of  the  top  of  a  car  or  locomotive. 

High -voltage  Signal. — A  signal  operated  by  a  current  of  usually  110  volts 
or  more. 

Highway  Crossing. — The  intersection,  at  the  same  elevation,  of  a  public 
highway  and  a  railway  line. 

Highway  Crossing  Protection. — An  arrangement  of  one  or  more  highway 
crossing  signals. 

Highway  Crossing  Signal. — An  audible  or  visual  signal  at  a  highway 
crossing,  designed  to  warn  the  users  of  the  highway  that  it  is  unsafe  to  pro- 
ceed over  the  railway  line. 

Hold  Clear  Attachment. — An  attachment  to  a  signal  mechanism  for 
holding  the  signal  in  the  clear  position. 

Home  Block  Signal. — A  fixed  signal,  located  at  the  entrance  of  a 
block. 

Home  Interlocking  Signal. — A  fixed  signal  at  a  point  at  which  trains  are 
required  to  stop  when  the  route  is  not  clear. 

Home  Signal. — A  fixed  signal  located  at  the  point  at  which  trains  are 
required  to  stop,  as  distinguished  from  a  distant  signal,  at  which  the  maxi- 
mum limitation  on  speed  is  a  response  to  a  caution  indication. 

Home  Track  Circuit. — A  track  circuit  situated  between  a  home  signal  and 
the  advance  block  signal,  which  governs  the  indication  of  the  home  signal. 


APPENDIX  353 

Hookgear. — A  device  by  which  one  lever  operates  one  of  two  pipe- 
connected  signals,  depending  upon  the  position  of  the  switch. 

Horizontal  Chain  Wheel. — A  chain  wheel,  the  axis  of  which  is  vertical. 

Horizontal  Locking. — Locking,  a  cross  section  of  which  lies  in  a  horizontal 
plane. 


__  Impedance  Bond. — A  low-resistance  bond,  making  a  continuous  path  for 
return  propulsion  current,  while  impeding  from  one  track  circuit  to  another 

the  flow  of  the  alternating  current  used  in  signaling,  and  confining  the  flow 
of  that  current  to  one  track  circuit. 

Impedance  Coils. — A  term  sometimes  applied  to  choking  coils  or  reactance 
coils. 

In  Advance  of. — Ahead  of,  as  related  to  an  approaching  train. 

Indication. — The  information  or  command  conveyed  by  the  aspect  of  a 
visual  signal.  The  information  conveyed  to  the  operator  of  an  interlocking 
machine  that  the  movement  of  an  operated  unit  has  been  completed,  and 
that  the  unit  is  in  the  full  normal  or  full  reverse  position. 

Indication  Lock. — An  electric  lock  fitted  to  a  lever  of  an  interlocking 
machine  for  the  purpose  of  preventing  the  return  of  that  lever  to  its  full 
normal  latched  position  until  it  is  released  through  an  impulse  of  current  in 
the  lock  coils. 

Inductive  Bond. — See  impedance  bond. 

Insulated  Rail  Joint. — A  rail  joint  in  which  insulating  material  is  placed 
between  the  ends  of  two  rails  and  around  the  parts  of  the  joint  so  as  to 
prevent  the  passage  of  electric  current  from  one  rail  to  the  other. 

Interlocking.— An  arrangement  of  switch,  lock  and  signal  appliances  so 
inter-connected  that  their  movements  must  succeed  each  other  in  a  pre-~ 
determined  order. 

Interlocking  Machine. — An  assemblage  of  levers  and  locking  in  a  frame, 
with  connections  arranged  so  that  the  levers  can  be  moved  or  unlocked  only 
in  a  certain  predetermined  order,  and  so  that  a  movement  of  a  lever,  or  its 
unlocking  preparatory  to  its  movement,  may  be  made  to  lock  any  or  all 
other  levers  in  the  frame. 

Interlocking  Plant. — An  assemblage  of  switch,  lock,  and  signal  appliances 
interlocked. 

Interlocking  Relay. — A  relay  comprising  two  sets  of  coils  and  then- 
armatures,  so  arranged  that  either  armature  may  be  made  to  prevent  the 
other  from  closing  or  opening  a  circuit  through  a  back  or  front  contact. 

Interlocking  Signals. — The  fixed  signals  of  an  interlocking  plant. 

Interlocking  Signal  Oil  Pipe. — A  pipe  which  is  filled  with  oil  and  provided 
with  stuffing  boxes  to  prevent  the  escape  of  the  oil,  and  containing  an 
operating  pipe  or  wire  used  in  mechanical  interlocking. 

Interlocking  Station. — A  place  from  which  an  interlocking  plant  is 
operated. 

Interlocking  Unit. — Any  signal,  switch,  derail,  lock  or  crossing  bar  oper- 
ated separately  or  in  combination  with  any  other  constituent  part  of  an 
interlocking  system. 


354  RAILWAY  SIGNALING 


Jaw. — A  forked  attachment  on  a  pipe  line  for  making  a  pivotal  connection 
to  another  pipe  line,  or  to  any  device. 

Jaw  Rod. — A  rod  having  a  jaw  at  either  or  both  of  its  ends  as  an  integral 
part  thereof. 

Johnson  Interlocking  Machine. — An  interlocking  machine  with  the  lock- 
ing bars  and  tappets  arranged  in  a  vertical  plane  beneath  it. 

Jumper. — A  temporary  shunt  or  short-circuit  in  a  series-connected  circuit, 
commonly  used  in  track-circuit  work  to  preserve  the  continuity  of  the  track 
circuit  past  a  section  of  track  such  as  a  crossing  or  electrified  tracks  where 
the  wires  cannot  be  suitably  insulated. 

Junction  Box. — A  box  to  which  are  run  a  number  of  electrical  conductors 
for  convenient  connection,  disconnection,  or  inspection. 


Lag. — The  phase  difference  of  one  alternating  current  behind  another,  or 
of  one  function  of  an  alternating  current  behind  another,  as  current  and 
voltage. 

Lap  Sidings. — An  arrangement  of  two  side  tracks  the  ends  of  which  overlap 
each  other. 

Latch  Block. — A  block  fastened  to  the  lower  extremity  of  a  latch  rod,  and 
which  engages  with  a  square  shoulder  of  the  segment  or  quadrant  of  a  me- 
chanical interlocking  machine  to  hold  the  lever  in  position. 

Latch  Foot. — The  connection  on  the  lower  end  of  the  latch  rod  in  a  me- 
chanical interlocking  machine  by  means  of  which  the  rocking  link  is  actuated. 

Latch  Handle. — The  part  of  a  lever  latch  which  is  grasped  by  the  hand  to 
operate  the  latch. 

Latch  Locking. — The  arrangement  of  mechanical  locking  in  which  the 
locking  bars  are  driven  by  means  of  and  through  connections  to  the  latches 
of  the  levers. 

Latch  Rod. — The  rod  extending  between  the  latch  handle  and  the  latch 
block  on  the  lever  of  a  mechanical  interlocking  machine. 

Latch  Shoe. — The  casting  by  means  of  which  the  latch  rod  and  the  latch 
block  are  held  to  a  lever  of  a  mechanical  interlocking  machine. 

Lattice  Post. — A  signal  mast  or  post  built  up  of  several  uprights  which  are 
fastened  together  by  diagonal  pieces  of  iron. 

"Lazy  Jack"  Compensator. — A  compensator  in  which  an  arm  of  an 
acute-angle  crank  is  so  connected  to  an  arm  of  an  obtuse-angle  crank  that 
the  two  connected  arms  move  in  the  same  general  direction  in  overcoming 
the  effects  of  expansion  and  contraction  in  lines  of  pipe  connected  to  the 
opposite  arm. 

Leadout. — The  arrangement  of  apparatus  by  means  of  which  the  motions 
of  the  levers  in  a  mechanical  interlocking  machine  are  transmitted  to  the 
pipe  and  wire  lines  outside  the  interlocking  station. 

Lever  Latch. — A  spring-actuated  mechanical  device  attached  to  the  lever 
of  an  interlocking  machine  to  hold  it  in  the  normal  or  reversed  position. 

Lever  Locking. — The  arrangement  of  mechanical  locking  in  which  the 
locking  is  connected  directly  to  the  levers. 


APPENDIX  355 

Lever  Shoe. — The  casting  which  serves  as  a  bearing  for  the  lever  of  a 
mechanical  interlocking  machine,  and  also  as  a  socket  for  one  or  more  tail 
levers. 

Line  Circuit. — The  wires  or  other  conductors  in  the  main  line  of  a  circuit. 

Lightning  Arrester. — A  device  to  prevent  or  reduce  the  possibility  of 
damage  to  electrical  apparatus  from  discharges  of  lightning. 

Link. — A  short  piece  of  1%-in.  iron  with  a  solid  jaw  at  one  end  and  a  screw 
jaw  at  the  other. 

"Lock-and-block." — A  common  name  for  the  controlled  manual  block 
system. 

Locking. — A  mechanical  arrangement  of  locking  bars,  dogs,  and  cross- 
locking  by  means  of  which  the  interlocking  is  effected  between  the  levers  of 
an  interlocking  machine  and  the  order  of  their  movement  is  determined. 

Locking  Bar. — A  bar  to  which  locking  dogs  are  attached  and  which 
extends  lengthwise  in  an  arrangement  of  mechanical  locking. 

Locking  Bracket. — A  bracket  which  is  part  of  a  locking  bed  and  forms  one 
of  the  supports  of  an  arrangement  of  mechanical  locking. 

Locking  Dog. — A  block  which  is  attached  to  a  locking  bar  or  tappet,  by 
means  of  which  the  locking  between  bars  is  accomplished. 

Locking  Filler. — A  filler,  placed  in  a  spare  space  of  a  locking  guide  to 
prevent  the  buckling  of  the  locking  bar  or  bars  in  the  adjacent  space. 

Locking  Frame. — The  whole  supporting  frame  of  an  arrangement  of 
mechanical  interlocking. 

Locking  Plunger. — A  plunger  of  a  mechanical  locking  device  which  passes 
through  an  opening  in  a  lock  rod. 

Locking  Sheet. — A  statement  in  tabular  form  of  the  locking  operations 
provided  for  a  given  interlocking  machine. 

Lock  Rod. — A  rod  which  is  connected  to  switch  points  through  which  a 
locking  plunger  extends  when  the  points  are  in  the  full  normal  or  full  reverse 
position. 

"Locking -up"  Track  Circuit. — A  track  circuit  used  to  take  away  the 
unlock  when  a  train  passes  an  advance  block  signal  into  the  block  ahead. 

Lower  Quadrant. — One  of  the  quarters  of  a  vertical  circle  below  its 
horizontal  axis. 

Lower  Quadrant  Signal. — A  semaphore  signal,  the  arm  of  which  is 
inclined  downwardly  from  the  horizontal  to  give  indications. 

• 
M 

Machine  Frame. — The  support  for  an  interlocking  machine. 

Machine  Framing. — The  frame  in  an  interlocking  station  on  which  the 
interlocking  machine  rests;  usually  set  on  a  foundation  separate  from  that 
which  supports  the  wall  of  the  building. 
'    Maintain. — To  keep  in  satisfactory  condition. 

Maintainer. — A  person  whose  duty  it  is  to  keep  signaling  apparatus  in  its 
proper  working  order. 

Manual  Block  System, — A  block  system  in  which  the  block  signals  at  a 
block  station  are  moved  by  hand  by  an  attendant,  on  information  conveyed— 
to  him  from  adjacent  block  stations. 


356  RAILWAY  SIGNALING 

Mast. — The  upright  from  which  signals  are  displayed. 

Mechanical  Bolt  Lock. — A  mechanical  device  connected  to  a  unit  in  order 
to  insure  that  one  or  more  other  units  are  in  their  proper  relative  positions. 

Mechanical  Interlocking. — Interlocking  in  which  the  units  are  operated 
manually. 

Mechanical  Locking; — See  Locking. 

Mercury  Contact  Relay. — A  relay,  the  armature  of  which  closes  one  or 
more  circuits  by  making  a  contact  through  mercury. 

Mechanical  Slot. — A  device  placed  in  the  connections  to  a  signal  which 
requires  the  movement  of  more  than  one  operating  lever  to  clear  the  signal. 

Mechanical  Time  Lock. — A  mechanical  device  in  connection  with  an 
interlocking  signal  lever  to  insure  a  time  interval  between  throwing  the 
signal  to  stop  and  moving  a  derail  or  switch  over  which  that  signal 
governs. 

Mechanical  Trip. — A  term  used  to  denote  a  trip — as  used  in  apparatus  for 
stopping  trains  without  the  intervention  of  an  engineman — which  is  actu- 
ated or  controlled  by  mechanical  means  as  distinguished  from  apparatus 
in  which  electricity  or  magnetism  is  employed  for  the  same  purpose. 

Mechanism. — A  general  term  for  any  mechanical  or  power  operated 
device  for  operating  a  signal  or  interlocking  function  or  accessory  device, 
from  a  distance. 

Mechanism  Case. — The  housing  for  a  signal  mechanism. 

N 

Neutral  Relay. — A  relay  in  which  the  flow  of  current  in  either  direction 
through  the  magnet  coils  has  the  same  effect  on  the  armature. 

Normal. — The  position  in  which  a  lever  in  an  interlocking  machine  stands 
when  the  corresponding  switch  or  signal  is  in  its  normal  position. 

Normal  Danger. — A  term  used  to  express  the  normal  condition  of  the 
signals  in  a  system  in  which  the  indication  to  proceed  is  given  only  upon  the 
approach  of  a  train  to  an  unoccupied  block. 

O 

Obtuse -angle  Crank. — A  two-arm  crank,  the  arms  of  which  subtend  an 
angle  of  more  than  90  degrees. 

Opposing  Train. — A  train  running  in  a  direction  contrary  to  that  of  any 
specified  train 

Outlying  Switch. — A  switch  not  connected  with  an  interlocking  plant. 

Overlap. — An  extension  of  track  circuit  control  of  the  signal  at  the 
entrance  to  a  block  through  a  portion  or  all  of  the  block  in  advance. 

Overstroke. — The  excess  throw  in  a  pipe  or  wire  line. 


Permissive  Block  Signaling. — The  method  of  signaling  which  permits  one 
or  more  trains  in  the  same  direction  to  enter  a  block  section  before  the  last 
preceding  train  has  passed  out. 


APPENDIX  357 

"Pick  Up." — The  point  in  the  gradual  increasing  of  the  amount  of  current 
flowing  through  the  coils  of  an  electro-magnet  at  which  the  amount  or  value 
of  the  current  is  such  as  to  overcome  the  force  of  gravity  on  the  armature, 
and  attract  it  against  the  cores  of  the  magnet  coils. 

Pinnacle. — A  casting,  usually  ornamental,  which  is  placed  on  top  of  a 
signal  mast. 

Pipe  Adjusting  Screw. — A  device,  used  in  a  pipe  line  for  changing  its 
length. 

Pipe  Carrier. — A  device,  comprising  a  grooved  roller  working  in  a  stand 
for  supporting  a  pipe  line  at  an  interlocking  plant  in  such  a  manner  as  to 
permit  of  its  longitudinal  movement. 

Pipe  Carrier  Bearing  Plate. — A  plate  or  bar  to  which  pipe  carriers  are 
fastened. 

Pipe  Carrier  Side  Plate. — A  part  of  a  pipe  carrier  which  passes  down  the 
side  of  the  pipe  and  is  secured  to  the  foundation  to  form  a  support  for  the 
rollers. 

Pipe  Carrier  Stand. — The  supporting  frame  of  a  pipe  carrier. 

Pipe  Connected. — The  condition  of  being  connected  together  by,  or 
arranged  for  operation  by  means  of,  a  pipe  line. 

Pipe  Line. — A  line  of  pipe  connecting  a  mechanically  operated  switch, 
or  signal,  or  other  operated  unit  to  its  lever  in  an  interlocking  machine. 

Pipe  Plug. — A  plug,  consisting  of  a  short  section  of  rod  which  is  inserted 
in  and  riveted  to  the  contiguous  ends  of  pipe  at  a  joint  in  a  pipe  line. 

Pipe  Run. — An  assemblage  of  pipe  lines  with  their  carriers  and  founda- 
tions in  a  common  course. 

Pit. — A  depression  below  the  floor  level  of  an  interlocking  station,  in 
which  part  of  the  leadout  apparatus  is  situated. 

Plunger;— The  bar  which,  by  entering  a  hole  in  the  lock  rod,  effects  the 
locking  in  a  facing  point  lock. 

Plunger  Box. — The  casting  or  guide  in  which  the  plunger  of  a  bridge  lock 
or  bolt  lock  moves. 

Plunger  Casting. — A  stand  and  guide  for  facing  point  and  bridge  lock 
plungers  and  lock  rods. 

Plunger  Release  Track  Circuit. — A  track  circuit  by  means  of  which  the 
plunger  of  a  block  signal  instrument  or  controlling  apparatus  is  released. 

Plunger  Stand. — That  part  of  a  facing  point  lock  which  is  secured  at  a 
certain  fixed  distance  from  the  switch  point,  and  through  which  the  plunger 
moves. 

Pneumatic  Interlocking  Diaphragm  Valve. — A  valve  controlling  the 
admission  of  compressed  air  from  an  operating  pipe  into  a  switch  or  signal 
cylinder. 

Pneumatic  Interlocking. — Interlocking  in  which  the  units  are  operated 
and  controlled  by  compressed  air. 

Point  Lug. — A  lug  bolted  to  the  web  of  a  switch  point  rail  to  which  the 
switch  rods  are  attached. 

Point  Rail. — Either  of  the  two  movable  rails  in  a  "split"  switch,  as  dis- 
tinguished from  the  immovable  "stock"  rails. 

Polarized  Relay. — A  relay,  the  operation  of  which  is  controlled  by  the      7  /t 
direction  of  the  flow  of  current  through  its  magnet  coils. 


358  RAILWAY  SIGNALING 

Polarized  Track  Circuit. — A  track  circuit  in  which  the  direction  of  current 
is  used  to  govern  the  polarity  of  magnetism  in  relay  magnets  for  the  control- 
ling of  apparatus. 

Pole  Changer. — A  device  by  which  the  direction  of  current  flow  in  an 
electrical  circuit  may  be  changed. 

Pole  Piece. — That  part  of  the  core  of  an  electro-magnet  which  projects 
beyond  the  coil,  and  adjacent  to  which  the  armature  is  placed. 

Polyphase  Relay. — A  relay  designed  to  respond  to  polyphase  alternating 
current. 

Position  Signaling. — A  scheme  of  signaling  whereby  the  information  to 
be  delivered  by  a  signal  is  shown  by  the  relative  position  which  the  moving 
part  of  a  signal  bears  to  a  certain  fixed  part. 

Pot  Signaling. — A  low  revolving  signal,  turning  on  a  vertical  axis,  and 
used  either  as  a  switch  target  for  indicating  the  position  of  the  switch  to 
which  it  is  attached,  or  as  a  dwarf  signal  for  low-speed  movements. 

Power  Interlocking. — Interlocking,  the  units  of  which  are  operated  by 
some  form  of  power  other  than  manual. 

Preliminary  Latch  Locking. — Mechanical  locking  so  arranged  that  the 
locking  of  a  lever  to  prevent  it  from  being  moved  in  conflict  with  another 
lever  is  fully  effected  before  that  other  lever  begins  to  perform  its  function. 

Propulsion  Bond. — A  rail  bond  which  will  carry  the  return  current  used 
for  propulsion  purposes  on  an  electric  railway. 

Pusher  Attachment. — An  attachment  to  electric  train-staff  apparatus 
designed  to  protect,  in  addition  to  the  regular  train  movement,  the  move- 
ment of  a  pusher  engine  when,  after  being  detached  from  the  rear  of  the 
train,  it  is  to  be  run  back  to  its  starting  point. 

Q 

Quadrant. — The  fourth  part  of  a  circle.  A  part  of  a  mechanical  inter- 
locking machine  which  is  bolted  to  the  machine  frame,  and  by  means  of 
which  all  levers  that  are  locked  by  another  lever  in  either  its  normal  or 
reversed  position,  are  held  locked  while  that  lever  is  being  moved. 

R 

Radial  Arm. — A  device  used  for  changing  the  direction  of  a  pipe  line. 

Rail  Bond. — A  metallic  connection  between  the  adjacent  ends  of  con- 
tiguous rails  in  a  track  to  insure  the  continuity  of  that  line  of  rails  as  an 
electrical  conductor. 

Rail  Clip. — A  metal  support  bolted  or  clamped  to  a  rail,  for  carrying  a 
detector  bar. 

Railway  Crossing. — The  intersection  at  the  same  elevation  of  two  or 
more  railway  tracks. 

Ramp. — A  bar  with  an  inclined  upper  surface  fixed  on  the  ties  of  a  railway 
track  and  designed  to  raise  a  vertically  moving  member  of  a  cab-signaling 
or  a  tram-stopping  system  depending  from  a  passing  locomotive. 

Reactance. — In  an  alternating  current  circuit,  the  component  of  imped- 
ance or  total  effect  retarding  the  flow  of  current  which  is  out  of  phase  with 


APPENDIX  359 

or  90  degrees  from  the  phase  of  the  current.  The  ohmic  effect  due  to  the 
induction  in  the  circuit. 

Reactance  Coil. — A  coil  for  producing  a  difference  of  phase.  A  magnetiz- 
ing coil  surrounded  by  a  conducting  covering  or  sheathing  which  opposes 
the  passage  of  rapidly  alternating  currents  less  when  directly  over  the 
magnetizing  coil  than  when  a  short  distance  from  it. 

Rear. — The  condition  of  being  behind,  as  a  train  in  relation  to  a  signal 
which  it  is  approaching.  A  term  used  to  describe  the  location  of  a  signal 
which,  with  reference  to  another  signal,  is  in  its  rear  when  it  is  in  such  posi- 
tion as  to  be  passed  first  by  an  approaching  train. 

Relay. — An  electro-magnetic  device  responsive  to  direct  and  alternating 
current  which  is  designed  to  repeat  in  one  or  more  electric  circuits  certain 
effects  of  changes  in,  or  completion  or  interruption  of  the  circuit  in  which  it 
is  placed. 

Relay  Armature. — The  movable  part  of  a  relay!  the  positions  oiovMch  are 
controlled  by  the  condition  of  the  magnet  coils  according  to  the  presence 
or  absence  of  current  therein. 

Relay  Post. — A  post  set  in  the  ground  to  support  a  relay  box. 

Relay  Shelter. — An  arrangement  for  housing  a  relay. 

Release. — An  arrangement  for  the  purpose  of  releasing  either  electrically 
or  mechanically  any  apparatus  which  has  previously  become  locked. 

Release  Route  Locking. — An  arrangement  for  releasing  the  route  locking 
at  an  interlocking  plant. 

Reverse  (verb). — To  move  a  lever  or  unit  in  an  interlocking  machine  from 
its  normal  to  the  opposite  position. 

Right-angle  Crank. — A  two-arm  crank,  the  arms  of  which  subtend  an 
angle  of  90  degrees. 

Riser  Plate. — An  iron  plate  riveted  to  a  tie  plate  at  a  switch  and  used  to 
support  the  switch  points. 

Rocker. — See  rocking  shaft. 

Rocking  Shaft. — A  shaft,  used  in  an  interlocking  plant  supported  on  two 
or  more  bearings,  and  rotated  about  its  axis  by  means  of  an  arm  at  one  end, 
thus  transferring  the  movement  to  an  arm  at  the  other  end.  A  shaft 
which  is  so  supported  as  to  transmit  motion  by  means  of  a  rotary  movement 
through  less  than  a  circle. 

Rocking  Link. — That  part  of  an  interlocking  machine  by  means  of  which 
the  latch  movement  is  transmitted  to  the  locking  bars. 

Roundel. — A  piece  of  glass  used  to  give  the  colors  to  the  night  indications 
of  semaphore  signals. 

Roundel  Clip. — A  device  made  of  rubber  for  holding  a  roundel  in  place 
between  the  semaphore  casting  and  the  roundel  ring. 

Roundel  Ring. — The  ring  by  means  of  which  a  roundel  is  held  in  place  in 
a  spectacle  casting. 

Route. — Any  path  or  course  which  can  be  taken  by  a  train  passing  from 
one  point  to  another. 

Route  Locking. — The  electric  locking  of  switches,  drawbridges,  etc.,  in  a 
route,  or  the  signals  of  a  conflicting  route,  to  maintain  the  integrity  of  a 
route  during  the  movement  of  a  train  over  it. 


360  RAILWAY  SIGNALING 

S 

Screw  Jaw.  —  A  jaw  fastened  by  means  of  a  screw  connection  to  the  pipe 
or  device  with  which  it  is  used. 

Screw  Release.  —  A  form  of  hand  release  operated  by  a  screw. 

Selective  Despatching  System.  —  A  system  in  which  a  number  of  audible 
or  visible  signals  located  along  a  railway  line  are  connected  to  a  telephone, 
telegraph  or  other  circuit,  and  in  which  any  one  of  such  signals  may  be 
operated  by  means  of  an  electric  selector  without  interfering  with  other 
signals  associated  with  such  circuit. 

Selector.  —  A  device  by  means  of  which  the  position  of  one  or  more  oper- 
ated units  may  be  made  to  determine  which  of  several  others  shall  be 
operated. 

Selector  Coil.  —  A  coil  which  when  energized  will  attract  and  hold  in  place 
an  armature  which,  in  turn,  will  permit  a  predetermined  movement  to  be 
made. 

Semaphore  Arm.  —  The  principal  movable  part  of  a  semaphore,  consisting 
of  a  blade  fastened  to  a  casting  which  turns  on  a  pivot. 

Semaphore  Bearing.  —  The  bearing  which  supports  the  pivot  of  a  sema- 
phore arm. 

Semaphore  Blade.  —  That  part  of  the  semaphore  arm  which  by  its  form 
and  position  gives  the  day  signal  indications. 

firnn«ftfrftf«  Siymqi.—  A  signal  in  which  the  indications  are  given  by  the 
positions  of  a  movable  arm. 

Semi-automatic.  —  The  condition  in  which  a  part  of  the  operation  of  a 
mechanism  or  device  is  accomplished  through  the  exercise  of  inherent  power 
of  motion. 

Semi-automatic  Signal.  —  A  signal  which  has  inherent  power  to  assume 
the  stop  position  after  it  has  been  cleared  by  other  means. 

Signal.  —  A  means  of  copv«YJa3[|frjn^^  ft 


Signal  Bracket.  —  A  column  or  post  with  an  offset  support  for  signal 
masts. 

Signal  Bridge.  —  A  bridge  which  spans  one  or  more  railway  tracks  for  the 
purpose  of  supporting  one  or  more  signals. 

Signal  Control.  —  The  arrangement  through  which  the  operation  of  a  signal 
is  governed. 

Signalman.  —  The  attendant  at  a  block  or  interlocking  station. 

Signal  Marker  Light.  —  A  light  used  to  distinguish  certain  fixed  signals. 

Signal  Mast.  —  The  upright  part  of  a  signal  which  is  used  to  support  the 
parts  of  the  signal  that  give  the  indication. 

Signal  Mechanism.  —  The  apparatus,  which  in  a  power-operated  signal 
directly  operates  to  change  the  aspect  of  the  signal. 

Signal  Repeater.  —  An  indicator  which  shows  in  a  cabin  the  changes  in 
position  in  the  arm  or  movable  disk  of  a  fixed  signal. 

S.  L.  M.  —  The  abbreviation  for  switch  and  lock  movement. 

Slot.  —  A  disconnecting  device  inserted  in  the  connection  between  a  signal 
arm  and  its  operating  mechanism. 

Slotted  Signal.  —  A  signal  in  which  the  connection  from  the  lever  or  other 
operating  mechanism  is  controlled  by  a  mechanical  or  electric  slot. 


APPENDIX  361 

Slow-acting  Relay. — A  relay  in  which  a  predetermined  time  interval  is 
made  to  elapse  between  the  opening  of  a  circuit  through  the  magnet  coils 
and  the  consequent  dropping  of  the  armature. 

Slow  Board. — A  sign  to  warn  the  enginemen  of  trains  to  reduce  speed  at  a 
certain  point. 

Slow -releasing  Slot. — An  electric  slot  for  an  automatic  signal,  so  con- 
structed as  to  consume  an  appreciable  interval  of  time  between  the  breaking 
of  a  circuit  and  the  consequent  releasing  of  the  holding  mechanism. 

Solenoid  Relay. — A  relay  hi  which  the  magnet  coils  are  solenoids  with 
movable  cores  upon  which  contacts  are  mounted. 

Smash  Signal. — A  signal  used  at  particularly  dangerous  points,  such  as 
drawbridges,  designed  to  be  broken  when  overrun. 

Solid  Jaw. — A  special  form  of  jaw  rigidly  connected  to  a  pipe  line. 

Space  Interval  System.— The  method  of  operating  trains  .>u  ^  to  main- 
tain certain  definite  relations  of  distance  between,  them. 

Spare  Lever. — A  lever  in  an  interlocking  machine  to  which  no  unit  is 
connected. 

Spare  Space. — A  lever  space  in  an  interlocking  machine  in  which  there  is 
no  lever. 

Spark  Gap. — The  air  space  or  gap  through  which  a  disruptive  discharge 


Special  Locking. — The  locking  on  an  interlocking  machine  arranged  for 
special  conditions. 

Spectacle. — The  casting  which  holds  the  glass  or  glasses  through  which 
the  night  indications  are  given  on  a  semaphore  signal. 

Speed  Control. — The  control  of  an  automatic  train-stopping  apparatus 
by  a  means  which  is  operative  or  inoperative  according  to  whether  the  speed 
of  the  train  is  or  is  not  above  a  certain  predetermined  rate. 

Spindle  Slot. — An  electro-mechanical  slot  attached  to  the  semaphore 
shaft  of  a  signal. 

Staff. — The  part  of  the  apparatus,  used  in  the  electric  train  staff  system  | 
the  possession  of  which  gives  enginemen  permission  to  enter  a  block. 

Staff  Catcher. — A  mast  equipped  with  a  device  for  receiving  a  staff  from 
a  moving  train  or  for  holding  a  staff  so  that  it  can  be  picked  up  by  a  moving 
train. 

Standard  Code. — The  code  of  interlocking,  block  signal,  and  train  rules 
adopted  by  the  American  Railway  Association. 

Stick  Relay. — A  relay  so  connected  that  a  circuit  through  the  magnet 
coils,  originally  closed  at  an  outside  point,  is  held  closed  through  a  contact 
of  the  relay. 

Stock  Rail. — Either  of  the  two  immovable  rails  as  distinguished  from  the 
movable  "point"  rails  in  a  split  switch. 

Straight-arm  Compensator. — A  compensator  which  is  in  the  form  of 
a  straight  connection  between  two  parallel  parts  of  a  pipe  line. 

Suspended  Signal. — A  signal  suspended  from  an  overhead  signal  bridge, 
or  other  high  structure. 

Switch  Adjustment. — An  arrangement  placed  on  the  front  rod  of  a  switch 
or  derail  so  as  to  provide  for  taking  up  any  extra  motion  which  the  pipe 
line  might  tend  to  impart  to  the  switch  or  derail. 


362  RAILWAY  SIGNALING 

Switch  Circuit  Controller. — A  device  for  opening  and  closing  electric 
circuits  of  block  and  interlocking  signals,  operated  by  a  connecting  rod 
attached  to  the  switch  points. 

Switch  Box. — A  common  name  for  a  switch  circuit  controller. 

Switch  Indicator. — An  electro-magnetic  device  controlled  by  a  track 
circuit,  to  indicate  whether  or  not  the  track  section  is  occupied  by  a  train. 

Switch  and  Lock  Movement. — An  arrangement  by  means  of  which  a 
single  stroke  of  a  lever  in  a  mechanical  interlocking  plant  unlocks  a  switch, 
moves  it  and  locks  it  again. 

Switch  Box. — A  circuit  controller  which  is  operated  in  conjunction  with 
the  movements  of  a  switch  and  is  usually  directly  connected  to  the  switch 
points. 

Switch  Point  Lug. — A  lug  attached  to  a  switch  point  to  which  the  front 
rod  is  connected. 


Tag. — A  label,  usually  in  the  form  of  a  disk  or  small  flat  piece  of  wood, 
fiber,  leather,  or  metal,  used  to  identify  wires,  wiring  connections,  or  parts 
of  apparatus. 

Tail  Lever. — The  part  of  the  lever  of  a  mechanical  interlocking  machine 
to  which  the  operating  pipe  or  wire  is  connected. 

Tang  End. — A  projection  on  the  end  of,  and  of  smaller  diameter  than,  a 
jaw  or  rod,  used  to  stiffen  the  joint  between  the  pipe  line  and  the  jaw  or  rod. 

Tappet. — A  bar  which  is  operated  directly  or  indirectly  by  the  lever  or 
lever  latch  in  an  interlocking  machine  with  vertical  locking  and  which  actuates 
the  locking  bars  and  is  locked  by  them.  A  pivot  or  swing-dog  which  is 
attached  to  the  locking  bar  in  an  interlocking  machine  with  horizontal 
locking,  and  which  is  actuated  or  locked  by  the  cross-locking. 

Tappet  Circuit  Controller. — A  circuit  controller  attached  to  a  tappet  and 
usually  operated  by  the  movement  of  a  lever  latch  handle. 

"T"  Crank. — A  crank  with  three  arms,  one  of  which  is  at  right  angles 
with  the  other  two  arms. 

Telegraph  Block  System. — A  block  system  in  which  the  signals  are  oper- 
ated manually,  upon  information  by  telegraph. 

Terminal. — Either  end  of  an  electrical  circuit,  or  the  device  or  apparatus 
to  which  it  is  attached.  The  end  of  a  line  or  system  of  railway. 

Three-light  Spectacle. — A  semaphore  spectacle  which  has  three  openings 
for  light  indications. 

Three -position  Automatic  Block  Signals. — A  system  of  automatic  block 
signals  designed  to  provide  the  protection  of  distant  signals  without  the 
duplication  of  signal  arms  usually  involved,  and  in  which  each  signal  is  so 
arranged  that  it  may  be  made  to  present  any  one  of  three  different  aspects. 

Three -position  Signal. — A  semaphore  signal  arranged  to  give  three 
different  indications. 

Throw  Rod. — The  rod  attached  to  the  head  rod  of  a  switch,  connecting 
the  switch  to  a  switch  stand,  pipe  line,  or  other  operating  device. 

Time  Interval  System. — The  method  of  operation  under  which  trains  are 
run  where  there  is  no  block  system. 


APPENDIX  363 

Time  Release. — See  Time  Lock. 

Time  Lock. — A  device  for  automatically  releasing  electric  locks  or  inter- 
locking levers  after  the  expiration  of  a  predetermined  time  interval. 

Torpedo. — An  auxiliary  stop  or  caution  signal  consisting  of  an  explosive 
cap  to  be  fastened  to  the  top  of  the  rail  of  a  track,  and  exploded  by  the  pres- 
sure of  a  wheel  of  an  approaching  locomotive  or  other  vehicle. 

Torpedo  Placer. — An  apparatus  for  placing  torpedoes  in  position  to  be 
exploded  by  the  passage  of  a  wheel  of  a  locomotive  or  other  vehicle. 

Torque. — The  movement  of  force  causing  rotation;  the  product  of  the 
force  and  the  distance  from  the  point  of  application  of  the  force  from  the 
center  of  rotation. 

To  the  Rear  of  a  Signal. — The  section  of  track  occupied  by  a  train  before 
it  has  passed  a  signal. 

Tower. — The  common  name  for  the  building  from  which  interlocking  and 
signals  are  operated.  See  Interlocking  Station. 

Track  Circuit. — An  electric  circuit  of  which  the  rails  of  a  track  form  a  part. 

Track  Circuit  Locking. — Electric  locking  which  is  accomplished  through 
the  medium  of  one  or  more  track  circuits. 

Track  Indicator. — A  map-like  reproduction  of  railway  tracks,  controlled 
by  track  circuits  so  arranged  as  to  indicate  automatically,  for  defined  sections 
of  track,  whether  or  not  such  sections  are  occupied. 

Track  Instrument. — A  lever  fixed  in  relation  to  the  rails  of  a  track  so  that 
its  deflection  by  passing  train  wheels  may  be  made  to  open  or  close  one  or 
more  electric  circuits. 

Track  Model. — See  Track  Indicator. 

Track  Relay. — A  relay  to  be  placed  hi  and  operated  by  a  circuit  of  which 
the  track  rails  are  an  integral  part. 

Train-order  Signal. — A  fixed  signal  used  at  telegraph  offices  to  indicate 
to  a  train  whether  or  not  it  must  stop  to  receive  orders. 


Train-order  Station. — A  station  where  train  orders  are  received  for  delivery 
to  trains,  and  where  trains  may  report  for  orders. 

Transverse  Pipe  Carrier. — A  pipe  carrier  designed  to  guide  pipe  across 
track. 

Trip. — In  automatic  tram-stopping  apparatus,  the  bar,  lever,  or  other 
device,  fixed  on  or  near  the  track  or  roadway,  which  when  in  a  certain  posi- 
tion trips  or  releases  the  apparatus  on  the  vehicle,  by  which  release  the  stop- 
ping of  the  vehicle  is  directly  or  indirectly  effected. 

Trunking. — The  wooden  casing  used  to  protect  both  electrical  conductor 
wires  and  those  wires  used  to  operate  signal  arms  when  they  lie  on  or  near 
the  surface  of  the  ground. 

Trunnion. — A  cylindrical  projection  on  a  revolving  part  for  supporting  it 
in  a  bearing. 

Tunnel  Signal. — A  signal  designed  to  be  placed  in  or  to  guard  a  tunnel. 

Two -light  Signal  Aspect. — A  semaphore  signal  which  shows  at  night  at 
least  two  lights. 

U 

Under  Control. — A  condition  in  which  an  engineer  is  prepared  to  stop 
within  the  distance  he  can  see  the  track  to  be  clear  ahead  of  him. 


364  RAILWAY  SIGNALING 

Up-and-down  Rod. — A  common  name  for  the  movable  vertical  rod  con- 
necting the  semaphore  signal  arm  with  the  operating  device  at  the  base  of  a 
signal  mast. 

Upper  Quadrant. — One  of  the  quarters  of  a  vertical  circle  above  its  hori- 
zontal axis. 

Upper-quadrant  Signal. — A  semaphore  signal  the  arm  of  which  is  inclined 
upwardly  from  the  horizontal  to  give  other  than  stop  indications. 

Universal  Link. — The  crank  arm  by  means  of  which  motion  is  transmitted 
from  the  rocking  link  to  the  rocking  shaft  in  an  interlocking  machine. 


Vane  Relay. — A  type  of  alternating-current  relay  in  which  a  light  metal 
disk,  or  vane,  is  caused  to  move  the  pole  pieces  of  magnets  to  close  contacts 
when  the  magnets  are  energized. 

Vertical  Locking. — Mechanical  Locking  arranged  in  a  vertical  plane. 

W 

Wheel  Stand. — The  frame  in  which  chain  wheels  are  supported. 

Wire  Adjusting  Screw. — A  device  in  a  wire  line,  used  for  changing  its 
length. 

Wire  Carrier. — A  device,  comprising  a  roller  or  pulley,  supported  in  a 
frame,  used  as  a  support  and  guide  for  a  wire  line. 

Wire  Compensator. — A  device  for  automatically  keeping  the  length  of  a 
wire  uniform  under  variations  in  temperature. 

Wire  Run. — In  an  interlocking  plant,  an  assemblage  of  wire  lines,  with 
their  carriers  and  foundations,  in  a  common  course. 

Wood  Capping. — The  covering  for  wooden  trunking. 


"Z"  Armature. — An  armature  of  an  electro-magnet  shaped  like  the  letter 
Z  and  used  in  enclosed  disk  signals,  indicators,  and  other  apparatus. 


INDEX 


Absolute  signal,  203 

staff,  190 

AGA  highway  signals,  315 
Air    supply,    electro-pneumatic 

system,  78 

Alternating    current,    block    signal- 
ing, 217-270 
double-rail  return,  222 
relays,  230 

signal  circuits,  237-248 
single-rail  return,  218 
interlocking,  121,  125,  132,  141, 

148 

A.  P.  Block  System,  260 
Approach  locking,  174 
Arresters,  lightning,  162 
Aspect,  signal,  8,  206,  325 
Automatic  block  signaling,  double 

track, 198-248 
single  track,  249-270 
Automatic  stops,  288 

B 

Back  locking,  43,  47 
Batteries,  157 

Battery  wells  and  chutes,  160 
Beam  light  signal,  299 
Bell,  crossing,  304 
Block    Signal    and    Train    Control 
Board,  7 

signal  circuits  (see  Circuits) 
Bolt  lock,  60,  63 
Bonds,  impedance,  224 

rail,  152 

Bracket  signal,  19,  20,  70,  202 
Brackets,  39 
Bridge  couplers,  74 

interlocking,  30 

lock,  75 

signal,  18,  70 
Bureau  of  Safety,  7 


Cable  posts,  160 

Calling-on  arm,  73 

Cells,  158 

Center-fed  track  circuits,  223 

Centrifugal  relay,  233,  236 

Channel  pin,  154 

Chart,  dog,  44 

Check  locking,  179 

Chicago,  Milwaukee  &  St.  Paul  Ry., 

270 

Chutes,  battery,  160 
Circuit  controllers,   indication,    90, 

111,  130,  141,  148 
switch,  126,  215 
Circuits,  controlled-manual,  188 
electric     interlocking,     Federal 

Signal  Co.,  141 
General  Railway  Signal  Co., 

107,  108,  117-121 
Hall   Switch   &   Signal    Co., 

146-148 
Union  Switch  &  Signal  Co., 

125-132 

electric  locking,  166-180 
electro-pneumatic  interlocking, 

92-97 

fouling,  151 

highway    crossing    signal,  SOS- 
SIS 

interlocking  (see  Electric  inter- 
locking) 

signal,  automatic  block  A.   C. 
double    track    two-posi- 
tion, 237-240 
L.  I.  R.  R.,  239,  240 
N.Y.N.H.&H.R.R.,242 
N.  Y.  Subway,  238 
West  Jersey  &  Sea  Shore 

R.  R.,  241 

D.    C.   double    track,    curve 
protection,  215,  216 


365 


366 


INDEX 


Circuits,  signal,  D.  C.,  normal  dan- 
ger, 213 

switch  protection,  215,  216 
three-position,  211-213 
two-position,  208-211 
single  track,  General  Railway 

Signal  Co.,  259-262 
other  installations,  262-270 
Chicago,    Milwaukee    & 

St.  Paul  Ry.,  270 
Cleveland,  Southwestern 
&  Columbus  Ry.,  259 
Norfolk  &  Western  Ry., 

267 
Northern  Pacific  R.  R., 

261 
Puget     Sound     Electric 

Ry.,  266 

Washington,     Baltimore 
&     Annapolis     Elect. 
R.  R.,  252 
Union  Switch  &  Signal  Co., 

249-259 

three-position,  240-248 
Cumberland  Valley  R.  R., 

244 
N.  Y.  Municipal  Railway 

Corporation,  246 
Southern  Ry.,  245 
Union  Switch  Signal  Co., 

243 
signal    mechanism,    model  2A, 

281,  282 

style  "B,"  273,  274 
style  "T-2,"  278 
staff,  190-193 

switch  (see  Electric  interlocking) 
track,  steam  roads,  D.  C.,  149, 

150 

A.  C.,  227 
electric  roads,  218-220,  222- 

224 

Cleveland,  Southwestern  &  Colum- 
bus Ry.,  258 

Clock  work  time  release,  173 
Color-light  signals,  11,  288,  291 
Commissions,  Interstate,  7 
Public  Utilities,  7,  318 
State  Railroad,  7,  318 


Compensation  table,  55 
Compensators,  51,  56 
Compressor,  air,  79 
Controlled-manual  block,  187 
Couplers,  bridge,  74 
Couplings,  50 
Cranks,  horizontal,  57 

vertical,  49 
Cross  lock,  39 

protection,  119 
Crossing  bars,  66 

bell,  304 
Crossing,  single  track,  25,  27,  29,  30 

double  track,  27,  30 
Cumberland  Valley  R.  R.,  244 
Curve  protection,  214,  216 
Cut  sections,  150 


Deflecting  bar,  50 
Departmental  system,  3 
Derails,  24,  65 
Detector  bar,  60 
Detector  locking,  94,  171 
Disc  signals,  14,  271 
Distant  signal,  10,  24,  201 
Diverging  routes,  28,  29,  30 
Division  of  Safety,  I.  C.  C.,  7 
Divisional  system,  3 
Dog,  39 

chart,  44-46,  106 
Doll  post,  21 
Double-rail  return,  222 

track  diverging  routes,  30 
Drawbridge  interlocking,  31 

couplers,  74 
"D"  slide  valve,  87 
Dwarf  signal,  21,  69 

electric,  118 

electro-pneumatic,  98 

position-light,  301 


E 


Electric  interlocking,  Federal  Signal 

Co.  system,  135-143 
interlocking  machine,  135 
switch  machine,  138 


INDEX 


367 


Electric    interlocking,    switch    ma- 
chine control  .and    indica- 
tion circuits,  141 
General    Railway    Signal    Co. 

system,  102-123 
cross  protection,  119 
interlocking  machine,  103 
power  supply,  102 
signal  control,  116 
switch  machine,  108 
track  diagram,  122 
Hall  Switch  &  Signal  Co.  sys- 
tem, 144-148 
interlocking  machine,  144 
signal  circuits,  146 
switch  operation,  145 
Union    Switch    &    Signal    Co. 

system,  124-133 
interlocking  machine,  124 
power  supply,  124,  125 
"SS"  control,  131 
switch  movement,  128 
the  indicating  system,  127 
Electric  locking,  166-180 
Electric  train  staff,  189 
Electro-mechanical  interlocking, 

Federal  Signal  Co.,  143 
General    Railway    Signal    Co., 

123 
Union  Switch  and  Signal  Co., 

133 
Electro-mechanical  slot,  Hall  type, 

183 

Union  type,  180 
Electro-pneumatic  interlocking,  78- 

101 

advantages,  101 
air  supply,  78 
detector  locking,  94 
electricity,  80 
indication,  90 
interlocking  machine,  81 
sequence,  80 
signal  mechanism,  98 
signal  operation,  99 
"SS"  control,  94 
switch  mechanism,  87 
switch  operation,  94 
End-fed  track  circuits,  223 


F.  P.  L.,  26 

Facing  point  lock,  26,  59,  63 
Federal  Signal   Co.,   electric   inter- 
locking, 135-143 

electro-mechanical,  143 

signal,  285 

Flagman,  automatic,  303 
Fouling  circuit,  151 
Foundations,  58 
Frequency  relay,  233,  236 
Frog,  movable  point,  64 
Front  rod,  162 


Galvanometer  relay,  231,  232 
General  Railway  Signal  Co.,  A.  P. 

block  system,  259 
automatic  stops,  288 
controlled-manual    block    sys- 
tem, 187 

electric  interlocking,  102—123 
electro-mechanical  interlocking, 

123 

relays,  234 
semi-automatic  signal  control, 

115 

signals,  279,  293-296 
switch  machines,  108 
Ground  signals,  18 


H 


Hall  Switch  and  Signal  Co.,  electric 
interlocking,  144-148 

electro-mechanical  slot,  183 

signals,  271,  283,  284 
Hand  release,  173 
Hayes  derail,  65 
Head  rod,  62,  162 
Highway  crossing  signals,  302 

circuits,  305 
History  of  signaling,  1 
Hoeschen  bell  system,  308 
Home  signal,  9,  24,  201 
Horizontal  crank,  57 

locking,  38 


368 


INDEX 


Illuminated  track  diagram,  122 
Impedance,  226 
bond,  224 
coil,  220 

Indication  circuit  controller,  90,  130 
Indication  relays,  90,  127 
Indications,  blade,  8,  206,  325 
light,  11,  12,  247,  295,  300 
Power  Interlocking,  Federal  Sig- 
nal Co.,  141 
General  Railway  Signal  Co., 

106 

Hall  Switch  &  Signal  Co.,  148 
Union  Switch  &  Signal  Co., 

127 

position-light,  300 
Indicators,  switch,  214 

tower,  185 

Insulated  rail  joints,  151 
Insulated  rods,  62,  162 
Interlocking,  electric  .systems,  Fed- 
eral Signal  Co.,  135-143 
General  Railway  Signal  Co., 

102-124' 
Hall   Switch   &   Signal    Co., 

144-148 
Union  Switch  &  Signal  Co., 

124-133 

electro-pneumatic,  78—101 
general,  22-35 
mechanical,  36-77 
object  of,  22 

Interlocking  machines,  Electric,  Fed- 
eral Signal  Co.,  135 
General  Railway  Signal  Co., 

103 

Hall  Switch  &  Signal  Co.,  144 
Union  Switch  &  Signal  Co., 

124 

electro-mechanical,  Federal  Sig- 
nal Co.,  143 
General  Railway  Signal  Co., 

123 
Union  Switch  &  Signal  Co., 

133 

electro-pneumatic,  81 
general,  36 


Interlocking  machines,  mechanical, 
horizontal,       Saxby      and 
Farmer,  36 
vertical,  Johnson,  47 
National,  47 
Stevens,  48 
Style  A,  40 
relays,  306 
Interstate  Commerce  Commission,  7 


Jaws,  52 

Johnson  interlocking  machine,  47 


Lamp,  R.  S.  A.  Semaphore,  72 

Latch,  38 

Latch  locking,  39 

Lazy  Jack  Compensator,  53 

Leadout,  49 

Lightning  arresters,  162 

Light  signals,  11,  12,  247,  288,  295, 

300 

Location  of  signals,  19,  23,  199 
Lock,  bridge,  75 

electric,  166-180 

F.  P.  L.,  59 

time,  69 
Locking,  approach,  174 

check,  179 

electric,  166-180 

horizontal,  36 

route,  176 

Saxby  &  Farmer,  36 

section,  171 

sectional  route,  177 

stick,  177 

style  A,  40 

vertical,  40 
Locking  bed,  39 

bar,  38,  39,  40 
driver,  38 

details,  41,  44 

shaft,  38 
crank,  38 

sheet,  26 
Lock  rod,  63 
Locomotive  bell,  304 
L.  I.  R.  R.,  239,  240 


INDEX 


369 


M 

Manipulation  chart,  35 
Manual  block  system,  186 
Marker  light,  204 
Mechanical  interlocking,  36-77 
Morden  derail,  66 
Movable  bridge  couplers,  74 

interlocking,  30,  32 

locks,  74 
point  frog,  64 


X 


National  interlocking  machine,  47 
Neutral  relay,  152 
N.  Y.  Municipal  Railway  Corpora- 
tion, 246 

N.  Y.  N.  H.  &  H.  R.  R.,  242 
N.  Y.  Subway,  238 
Norfolk  &  Western  Ry.,  267 
Normal,  24 

Normal  clear  signals,  208 
Normal  danger  signals,  213 
Northern  Pacific  R.  R.,  261 
Numbering  signal  posts,  206     -    . 


Order  of  locking,  25 
Organization,  2 
Overlap  systems,  203 


Peabody,  J.  A.,  23 
Permissive  signaling,  203 
Permissive  staff,  194 
Pin  valve,  electro-pneumatic,  91 
Pipe  carriers,  50 
Pipe  lines,  55 
Pipes,  50,  52,  79 
Polarized  relay,  156 
Polarized  track  circuits,  209,  213 
Position-light  signals,  12,  299 
Posts,  cable,  160 
Pouches,  staff,  196 
Power  interlocking,  sequence  in,  80 
24 


Power  mains,  125 
Preliminary  locking,  39 
Puget  Sound  Electric  Ry.,  266 
Push  button,  85,  133 
Pusher  syaff,  197 


Quick  switch,  86 

R 

Radial  arm,  57 
Rail  bonds,  152 
Rail  joints,  151 
Reactance  (see  Impedance) 
Relays,  alternating  current,  230-237 

frequency,  233,  236 

indication,  90 

interlocking,  306 

neutral,  152 

polarized,  156 

posts,  160 

stick,  179 
Release,  hand,  172 

screw,  172 

slow,  173 

time,  173 

Resistance  grid,  219 
Reversed,  24 

Road  crossing  signals,  302 
Rocker-link,  38 
Rocking  shaft,  49 
Rod,  front,  162 

head,  62,  162 

insulated,  62 

lock,  63 

tie,  162 

Rosenberg,  C.  C.,  199 
Route  Jocking,  176 
Rules  for  foremen,  6 

signalmen,  75 

state  inspectors,  318 

supervisors,  5 

trainmen,  75 


s 

Saxby     and     Farmer 
machine,  36 
Screw  release,  173 


interlocking 


370 


INDEX 


Sectional  route  locking,  177 
Section  locking,  171 
Semaphore  lamp,  72 
Semaphore  signals,   9,    10,    67,    70, 
201-217,  238-245,  249-268, 
272-287 

Sequence  in  power  interlocking,  80 
Setting  section,  170 
Shaver,  A.  G.,  3 
Sheet,  locking,  26 
Siding  protection,  214 
Signal  aspect,  8,  206,  325 
batteries,  157 
bridge,  18 
cell,  158 

circuits  (see  Circuits) 
control,   electro-pneumatic,  99, 

100 
electric,  Federal  Signal  Co., 

136 
Hall  Switch  &  Signal  Co., 

146,  148 
General   Railway   Signal 

Co.,  115,  118 
Union  Switch  &  Signal  Co., 

131 

engineer,  3 
indications,  8 
light  indications,  11 
location,  19,  23,  199 
mechanism,  color-light,  291 
electro-pneumatic,  275 
Hall  disc,  271 
Hoeschen,  308 
light,  288,  291 
model  2A,  279 
position-light,  299 
style  "B",  272 
style  "K",  283 
style  "L",  284 
style  "S",  275 
style  "T",  276 
subway,  297 
tunnel,  297 
type  "4",  285 
numbers,  206 

operation,  98,  115,  131,  148 
organization,  2 
Signaling,  purpose  of,  1,  198,  249 


Signals,  disc,  14,  271 

dwarf,  21,  69,  98,  118,  301 
light,  color,  11,  288,  291 

position,  12,  299 
semaphore,  9,  10,  67,  70,  272- 

287 

Single-rail  return,  218 
Single-track  crossing,  25-30 

signaling,  249-270 
Slip  switch,  64 
S.  L.  M.,  26,  59 
Slot,  electro-mechanical,  Hall,  183 

Union,  180 
Slow  release,  *173 
Southern  Ry.,  245 
South  Station,  Boston,  78 
Special  locking,  26,  39,  42 
"SS"  control,  94,  131 
Staff,  electric  train,  189 

catcher,  194 

Stevens  interlocking  machine,  48 
Stick  locking,  177 

relay,  179 

Stops,  automatic,  288 
Stuffing  box,  52 
Style  A  locking,  40 
Subway  signals,  238,  246,  294,  297 
Swing  bridge  couplers,  74 

dog,  39,  43 
Switch,  63 

adjustment,  62 

and  lock  movement,  26,  59,  87 
box,  215 

circuit  controllers,  126,  215 
indicators, '214 

lever  wiring,  92,  107,  141,  147 
machine,  electro-pneumatic,  87 
Electric,  Federal  Signal  Co., 

138 
General    Railway   Signal 

Company,  108-114 
Hall  Switch  &  Signal  Co.,  145 
Union  Switch  &   Signal  Co., 

128 

magnets,  88 
movements,    94,  108,  128,  138, 

141 

protection,  214,  216 
valve,  87 


INDEX 


371 


Switchboard,  102 
Symbols,  R.  S.  A.,  330 


Take  siding  indicators,  16 

signal,  17 
Tappet  bar,  40 
TDB  system,  255 

Three-block  indication  scheme,  206 
Three-position,  semaphore  signaling, 

202 
signals,  10,  202,  275 

circuits,  211,  240,  259 
Tie  rod,  162 
Time  element  relay,  236 
Time  lock,  69 

release,  173 
Tower  indicator,  185 
Track  batteries,  157 

circuits,    steam    roads,    direct 

current,  149 
alternating  current,  227 
electric  roads,  D.  C.  propul- 
sion,   single-rail    return, 
218 

double-rail  return,  222 
A.  C.  propulsion,  227 
diagram,  34,  122 
Trailing  point  crossover,  29 
Train  staff,  189 
Transformers,  222,  228 
Transmission  line,  217 
Trunking,  161,  163 
Two-position,  distant  signal,  10,  201, 

208 

home  signal,  9,  201,  208 
polarized  track  circuits,  209 
semaphore  signaling,  201 
signal  circuits,  208,  237 
Type  "F"  interlocking  machine,  124 


U 

Unbalancing  of  current,  225 
Union  Switch  &  Signal  Co.,  Electric, 
Type  "F"  system,  124-133 
electro-mechanical  interlocking, 

133 

electro-mechanical  slot,  180 
electro-pneumatic  interlocking, 

78-101 
flagman,  303 
relays,  155,  230 
signals,  272,  292,  294,  297 
single     track     systems,     TDB 

system,  249 
Universal  link,  38 


Vane  relay,  230 
Vertical  crank,  49 
locking,  40,  43 

W 

Washington,  Baltimore  &  Annapolis 

Electric  R.  R.,  252 
Wells,  battery,  160 
West  Jersey  &  Seashore  R.  R.,  241 
Wigwag  signal,  303    . 
Wire  compensator,  56 
Wiring  diagram  (see  Circuits) 


''X"  springs,  94 


"Y"  springs,  94 


Z  armature,  271 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED  \ 

rrnwp   I  IROAPV 

:i.:.i'.iiiU    LlDlA/ml 


Tel.  No.  642-3339 

This  book  is  due  on  the  last  date  stamped  below,  or 
on  the  date  to  which  renewed. 


^AftP^H 

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